You have my greatest sympathies! This was one of the hardest thing to do for my daughter (23months) and although it still isn't great, it's getting better! i tried her standing on a stool over the basin so she could look in the mirror but gave up, because I also had to hold her up! Now we both sit on a cushion each on the floor. We do it in the morning every day after breakfast, before she gets dressed for the day, so she is not tired! We 'brush her smile' first, then I do the back and sides, although it's pretty quick, I get to touch on each tooth, which is a big improvement for us! I sometimes sing and talk about things like Dorothy having big white teeth to clean (Wiggles). After I have a brush, it's her turn. The biggest thing I've found is letting go of my frustration, and accepting whatever happens, and knowing when to stop trying so it doesn't become to stressful! Keep trying, breath deep and it will get better! But it is a huge challenge!!!