Every day, pick him up, love him, and touch his feet. Mess with his
toes. If he is good, praise him like crazy. If he is bad, give him a
firm no, and hold him still for a minute. Nothing agressive, just firm
and consistent.

Jay Jay came as a shelter cat. He had not had his mails done before I
got him, that anybody knows about. The shelter only had him 2 weeks,
and his nails were pretty sharp when I got him. He looked surprised but
tolerated it.

After about 8 months, he decided he was safe in his new home, and he
could now argue about things he did not like. The first time, he
swatted the clippers out of my hand. Whacked them right across the
room. The second time, he kicked me hard and swatted at my hand,
resulting in a scratch.

My response? I held him for a couple minutes in an uncomfortable
position. I told him very firmly that we do this my way, and then I
finished his nails.

The next time, he tried a few kicks, and we took a few firm timeouts. I
started handling his toes avery day after that and praising him for
good behavior.  After that, all he does is pout. He has a very cute
miserable expression, but he does not kick or struggle in any way.