Brush them as soon as they come in...you should actually be wiping the gums with a facecloth before the teeth come in to rid the mouth of plaque. As for toothpaste and fluoride,I would check with your health dept as to the fluoride content of your water. If it's regulated at 1 part per million, then Iwould use toothpaste when your child has learned to spit it out....usually around age 3, and even then use only 1/2 a pea sized amount onthe tbrush. If you are on well water, have it tested. If the fluoride content is low, I woul use a teensy smear on the toothbrush once a day. I live in Canada, so things may be slightly different...check with your local Health Unit or Dental Office to see what their recommendation is.
Beth