"Uh, sure. I'd like to." Mike was surprised to hear himself say that, but then grinned sheepishly. "I mean, if you really don't mind."
"Sure!" Liam chuckled as he grabbed a wooden crate from the corner of the stall and dragged it over beside Mike. Then he climbed up, putting his genitals in easy reach.
Mike slid his hand over the coarse, warm sheath, and then gently stroked the ballsack with his fingers. "So, mine is like that?"
"Twice as big." Liam laughed. "Three times as big by the time I am done!" The teen ran his hand over Mike's chest, and then felt his nose and mouth with dirty fingers.
Mike could smell old manure, piss, dirt, straw, and other things. It was a good smell. He shifted on his hooves, aware of his own growing erection, and something else. He was still getting larger! Looking back, he realized the black hide and thicker body was still spreading down his sides and hind legs even though Liam was not brushing him. "You don't have to brush me?"
Liam shook his head. "Once I get it going, physical contact and desire are enough to make the change continue. And you have two of us working on you." He chuckled and tousled Mike's hair, and then pushed fingers into his nostrils. "Conner is looking for a mate, and I am looking for... well, a happy Shire." The fingers felt tight at first, but then Mike's nostrils relaxed and seemed to flare slightly. Liam pulled his fingertips out and pushed them into Mike's mouth, sliding them over his front teeth.
The fingertips tasted slightly bitter, probably from dirt and waste, but Mike allowed the intrusion because of the pleasant warmth and pulling he felt in his mouth and nose. After Liam pulled the damp fingers out, Mike reached up to feel his face. His lips felt thicker, his teeth larger, and his nose broader. "Why are you changing my face?" He was not upset or annoyed, just curious.
"Part of the package." Liam jumped down off the box. "But we'll get back to that later." He ran the brush along Mike's side, already covered in black hide. "Now for some real fun." He ran the brush under Mikes now-rigid cock and sheath, then set the brush down and used his hands to pull back the foreskin. Mike shivered at the pleasurable sensation - his horse cock was more sensitive than his human cock had been, and there was a lot more of it. As Liam continued to rub, Mike twisted as far around as he could and stared. The already massive horse penis was thickening and lengthening, and his swollen ballsack looked like it held pool balls! He was panting now, and felt pressure building. "Oh! Oh... wow... I think..." Then he arched back as he erupted with a jet of yellow-white semen that splattered the back of his forelegs and the floor, overwhelmed by a flood of instincts and primal sensations. Connor whinnied and bumped him.
Liam laughed. "Don't worry, girl. Plenty more where that came from."
Still panting, Mike looked at the teen incredulously. "More?" Granted, it had not taken long for the stableboy to bring him to climax, but there looked to be a cup of semen spread over the straw!
"Heck, yeah." Liam picked up the brush and used it on the backs of Mike's forelegs. The semen seemed to vanish into the bristles, and Mike had to shift as his forelegs lengthened. "You got a lot more coming."
The mare was lipping at Mike's human back and arm, and he resumed rubbing her neck. Looking around, Mike was surprised to find that he had gotten noticeably larger. In fact, as Liam continued to brush and pet his sides and legs, the centaur realized he was a little bigger than the Shire mare! Connor's scent had been horsey and pleasant before, but now it carried a strong undertone that kept his cock erect and made his testicles churn. Mike felt excited and happy, and a little bit confused. When Liam climbed back on the box, he grabbed the boy up in a hug, which Liam returned with a grin. Mike couldn't help himself - he felt a combination of affection and desire for the teen that overrode his normal reservations.