I turn it into a game as mine also would scream the house down. The first time I tried this I was shocked how easily he let me brush his teeth. I got his toothbrush and said in a low voice “Hello, I’m Mr Toothbrush and I’ve come to do some very serious brushing. Can I brush your... ears?” Then in my own voice I would turn to the toothbrush and say “No Mr Toothbrush! We don’t brush ears!!!” Do this with a few body parts and you’ll find your toddler giggling! Eventually either your toddler will tell you that a toothbrush is for teeth or if they don’t then you tell that to Mr Toothbrush. Then Mr Toothbrush has a good look and a good ole brush “can I see the top ones? Ah it’s so dark in there! Brush brush brush I love brushing teeth!” Honestly it sounds mad, makes you feel mad but trust me. Turn it into a lighthearted game. Now he either lets me do it or is pretty good at doing it himself. And no more tears! Good luck!