Debbie, there's a thread here with some tips that might help.
I don't use toothpaste for Yasin because if they swallow it the flouride can cause discoloured teeth. We have a bit of a battle here at times but I try not to get too tense about it - they do get a second set after all. I think the most important thing is setting up good habits not getting thier teeth squeaky clean IYKWIM.
Also in the few seconds I'm allowed of teeth cleaning time I try to get to the molars because they are more likely to get decay.