Even before his tooth peeks, it should be a daily habit for you to clean your baby’s gums. This will keep the bacteria from accumulating inside his mouth. Also, this will get him used to the routine.
What you need to do is simply wrap a soft cloth around your index finger and rub it gently over his tiny gums.
Then, as the teeth start to sprout, you can buy a very soft baby toothbrush. I use this cute brush that I can put on my finger. Yes. it has no handle. Available in malls and baby stores. I bought one for my baby just across a Fender Blacktop Stratocasters stall.
Put in a pea-size flouride toothpaste and massage it over his teeth. No need to rinse.
When you notice that the brush is splayed, replace it immediately so as not to damage his gums.