You can try "backwards chaining" to teach him how to brush. Basically, list out all of the steps it takes to brush teeth, and I'd add visuals to each step as well. Let's say you come up with 10 steps to brushing teeth. So then you do everything for him from step 1-9, and focus on having him learn the last step, step 10. Once he has that down, then you work on step 9, and he does step 10 on his own because he was able successfully get that step down; and so on for step 8, etc. The only opportunity he gets to do it by himself is that step you're working on and any steps he's accomplished. Good luck!

Finger toothbrush.......you may get bitten a few times but worth a try!!

I'm thinking of trying one of those three sided brushes to 1) clean my sons teeth better and 2) speed up the process. I see them all over the Internet...https://www.amazon.com/Surround®-Toothbrush

tooth brush song by story bots helped mine

Great ideas, thank you!