I'm seconding Patrick's suggestion here with our experience.
When we adopted Sammy he was around 3-5 y/o and likely had never been groomed.
He was in such bad shape that he'd been shaved down to the skin by the animal shelter that had seized him due to abuse & neglect. Anyway, all was easy as long as he had practically no fur & his nails were short.
But when everything started to grow back in, he wasn't too sure that he liked us so much after all. We were lucky that he's such a sweet lamb & didn't try to bite, but he looked very scared & stressed. We dealt with it by having my hubby & I take turns doing the brushing, while the other sat in front of Sam & petted him, praised him & fed him kibble after kibble after kibble! Honestly, that may just be how he gained his weight back so fast.
He really couldn't think about the brush or mat rake when there was something yummy in his mouth.
Nails weren't fun either, so my hubby would sit on a chair (without arms) and lift Sam into his lap with Sam's legs hanging down (looked like a fork lift
) and I'd sit on the floor under him & trim his nails while I fed him treats. This kept him still & the treats kept him happy long enough to get the job done. We also started out slowly, only 5 minutes or so at first, until Sam began to look forward to the treats & could tolerate longer without seeming too stressed. In time, it became something that though he probably still doesn't look forward to like Cassie & Daisy do. He doesn't seem to mind too much either.
If your boy is food or treat motivated, I'd definitely try this for him. Good luck & let us know how it's going.
