"Oh man, Roger, these weights are so heavy!" Adam exclaimed as he hopped around the room, letting the extra thick set of weights pull on his balls.
His still rigid cock bobbed up and down as it dribbled with the remnants of his most recent orgasm and he kept swishing his ass back and forth to wiggle the tail plug around in his hole. The special nanites embedded in the bulb of the butt plug were already going to work, shaping and reforming Adam's anus to make it more receptive to his new life as a donkey bro. His soft tissue was made more elastic to allow it to accept objects of almost unimaginable size yet it would always remain as tight and firm as it was now. The initial changes were also spreading to his tailbone which would make him ready to receive his permanent tail at the clinic the next day.
"The heavy weights are to get you used to how big your balls are going to get as a breeder, Adam. And would you stop fidgeting so much and clean up your mess." Roger commented while he busied himself with some of the other instructions in the box.
"Yes sir, I'll go get some rags." Adam said as he turned towards the door.
Roger wasn't sure it would work but he had to try, somehow he knew his big dumb brother wouldn't be able to say no. "Don't bother, Adam. Just use your tongue."
"What? You want me to lick up my own cum?" frowning Adam turned around with a disgusted look on his face.
"You heard me. now get going." Roger grinned maliciously.
Adam shook his head like he was going to resist but then seemed to think better of it before he dropped to his hands and knees and started lapping up the congealing puddles of cum from the hardwood floors. Roger watched as Adam crawled forward, his donkey tail swaying in the air over the muscular globes of his brother's butt.
"Make sure you get all of it, I don't want to have to walk around on sticky floors."
"Yes, master. Just please don't tell anybody about this. I'm not going to get any girls if they knew I have to do this." Adam whined.
Despite his protests, Roger noticed how much eagerly Adam was licking at his spooge now and his cock was fully hard again by the time he finished. "I don't think you'll need to worry about that bro." Roger responded as his brother got to his hooved feet. "Now come over here, the next step in the process you'll have to do yourself since I don't want to get any of your nanites on me."
Adam obediently stepped over to Roger who held out a small plastic tub. Lifting of the lid, Roger revealed that it contained a shimmering clear gel. "You need to rub this into the skin on your cock and balls, but I don't want you shooting another load all over my room so you better control yourself this time, donkey."
The concern was evident on Adam's face. His rigid cock was already pulsing in time with his heartbeat and a dollop of pre was already growing at the tip. It wasn't going to take much stimulation to get him to shoot his wad.
"Of course Roger, I'll do my best." He dipped several fingers into the tub and pulled out a great scoop of the goo.
The gel felt cold on his fingers but the instant it touched his cock it started to warm. A strong tingling sensation spread through his groin as he slid his touch down his shaft. He moved so very slow at first trying to keep his desires in check. The tingling only grew more intense as he traced a goo covered finger around his heavily weighted balls almost as if he could feel the churning of his spunk inside them. Adam worked his had up and down his shaft, working the nanite infuse gel into his skin and he began to moan in pleasure. He even let his other hand slide up his stomach, leaving a trail of gel behind, to reach up and tweak his pierced nipples.
"Hmmm, oh yeah. Hawwwww. Pleeease hawww, Please let me cum master!" Adam begged.
"No. you're not going to go blasting my room again. You're a wrestler though, you should be flexible enough, I think you know what you need to do." Roger said feeling his own pulse quicken at the sight of his muscle bound brother jerking himself in his room. His own cock was rock hard and leaking pre like mad into his tented shorts.
Wordlessly, Adam dropped to the floor, yelping as he sat down and drove his forgotten about tail plug deeper into his ass. With one hand still rapidly stroking his goo coated member, he laid back and then kicked his feet up into the air and brought them down over his head and putting his swollen cock head at his mouth. He licked his lips hesitantly at first but then he got a taste of the gel that had splashed there. Before he could even think, Adam's tongue was flashing out, slapping against his swollen prick as he pulled at it to milk even more juice from it's throbbing length. In one smooth motion he drove his cock deep into his own maw, thrusting his hips and working his head up and down ad he greedily sucked at his own cock.
Roger couldn't resist and he knelt down beside his brother and ran his hands across his up turned ass. He reached over and grasped the base of the tail plug protruding from between his ass cheeks and tugged on its ropey length. He jiggled the plug back and forth and seated it even deeper into Adam's rear. That last bit of stimulation was more than enough and Adam started to scream out with muffled brays as his cock erupted with a load even bigger than the one he had just minutes earlier. Blast after blast of thick cum coursed through his shaft which still tingled from the application of the goo, the massive amount of spunk filling his throat and Adam found he was all to eager to suck down every last drop. Roger felt his own meager orgasm dripping down his leg as he came at virtually the same time, never having touched his cock.
Eventually, the tide of spunk had stemmed and Adam withdrew his cock from his mouth and lay back on the floor panting. "Damn, that was incredible. What was that goo for anyway, Roger?"
Roger sat back down on his bed, his shorts a sticky mess, "Those bro, were the first application of nanites that will give you the proper donkey cock. I don't know that you were supposed to spread them all over your chest like that, or get them in your mouth for that matter."
"I'm sure it won't matter," Adam said rubbing a gel coated hand over his washboard abs. "If the first application was that good, I can't wait for the full treatment and I can get my donkey cock in some hot babes."
Roger laughed inwardly, this dumb jock really had no idea what donkey bros were primarily used for. If he had thought pony boys were pervs...
Adam managed to get himself back up, standing a little shakily in his hoof shoes, "Do you mind if I go clean up now master?"
"No time for that now, bro." Roger smiled, "we've got a busy day today before we go to the clinic tomorrow. First we have to..."