Here's what works for us when my daughter (same age) doesn't want to do something.
Our issue is nap time.
I taped a piece of construction paper to her bedroom door. Above that on another piece of paper I wrote the bed time rules:
Lay down
Close your eyes
Go to sleep
If she naps that day she gets a sticker on her paper and we let her watch a short video.
No nap-- no sticker no video. I just say, that's ok, I'm sure you'll nap tomorrow and then you can get your sticker and video.
The stickers don't mean anything, she just loves them.
Kids are so motivated by rewards.
You could do the same thing with morning and evening rules.
Eat breakfast
Wash your hands
Brush your teeth.
Something like that.
She also has a Thomas the Train toothbrush that sings to her.
Make sure you are using non fluoride toothpaste until 31/2 or so until they can spit.
My dentist recommended Tom's toothpaste in strawberry flavor. It's the same flavor for fluoride and non fluoride, so when you make the switch to fluoride she'll never know.
I would also suggest taking her to a pediatric dentist if you haven't already.
They are so good with kids that age.
Good luck!