Help with toddler teeth-brushing?

My son, just turned 2, really loves teeth-brushing time, which is great. The problem is that he is very independent and insists on cleaning them himself. He has a total meltdown if I even suggest helping him, let alone doing it for him. I've tried getting him to do my teeth while I do his, singing and dancing, brushing together etc but short of pinning him down and holding his nose (no I wouldn't!!!) I cannot get him to let me help. I don't want to stress him unduly or dampen his enthusiasm but I do worry about tooth decay. Should I just go with the flow until he's a little older and better able to understand and co-operate, or is there something else I can try?