When did you start brushing their teeth?

Hi. So I have an almost 1.5 yo who hates when I touch the insides of his mouth, ever since he was a baby. I thought that since he's been on solids for a while now that I should brush his teeth atleast every night.

When did you start and how do you do this with a wriggly toddler? Do you add toothpaste? Do they prefer that?

Edit: I wrote 2.5 yo instead of 1.5 yo!

Edit: And thanks everyone for your suggestions! Songs seem very popular! Just to also add that I use the silicone brush sometimes, it's just not a regular thing. I did buy a toothbrush and toothpaste too when he started teething, I should've just gone with my gut! Hopefully, it's not too late to start.