M.K.
We were also instructed to wipe our infants teeth with a washcloth after the last feeding as soon as a tooth came in. I introduced the toothbrush around 12 months or so. Definitely when they could stand up on their own.
Please do not use toothpaste with fluoride until your child is able to spit without any possibility of swallowing. Fluoride toothpastes carry poison warnings because swallowing more than a 5mg per kg of body weight can be toxic. I don't know when kids can spit without swallowing -- maybe 5 or 6??
I've decided not to use baby toothpaste (without fluoride) because I'm worried it will delay their ability to spit. It smells and tastes so good, I'm afraid they will enjoy "eating" it too much. But other Moms seem to like using it!