I used a toothbrush and some of that safe to swallow toothpaste right away, I say that its better to get him used to the feel of the toothbrush, trust me, with my daughter she screamed the whole time for the first year, don't use the washcloth/wipe off route, they need to get used to the feel of the bristles.
and make sure to find a good pedi dentist and ask when they want to see you son for the first time, if you get him used to the dentist early you won't have any fears or meltdowns as they get older, go every 6 mos and by the time they are old enough to understand he will be used to it, my son is 5 and has been going since he was a baby, and he isn't afraid at all. and my daughter is 2 and doesn't have much of a problem with it either...
good luck