R.F.
My nephew also hated having his teeth brushed. We just started asking him "Do you want to do this the easy way or the hard way?" and if he said easy way, he got to brush first, then mom got to finish up. If he didn't answer or said no, etc., mom ended up holding him down and brushing his teeth. He didn't like that much, and he learned really quickly that he wasn't going to get out of having his teeth brushed.
Monika's trick with the 'monkeys' sounds like it could work, too! I would try that first, then if that doesn't work, maybe try 'easy way or hard way' lol.