I was at the dentist last week and asked. Brush with water and toothbrush; no toothpaste. I didn't ask about when to start toothpaste, but will ask when I go back for my next appt.
We brush when we get ds dressed in the morning and putting pjs on at night. I then nurse and don't wake him to brush. We also don't remember to brush every day, but it gets done the majority of days.