Dogs can't have regular toothpaste mainly because of the flouride. There are many dog toothpastes out there (C.E.T. is a good one) that are chicken or beef flavored. Any soft bristled brush will do but there are some really great ones for dogs with a longer and ergonomic handle that are easier to use.
The vet I worked for was a big on teeth brushing and this is how we explained to the clients to get the dog used to it:
First few days just put a tiny bit of the dog toothpaste on your finger and let them lick it off followed by praise and a treat.
Next couple of days put the toothpaste on your finger and rub it on their teeth (like brushing with your finger) followed by a treat.
Then when they've accepted and are used to that, go ahead and use the brush - you want to start at the gum line and go in a downward motion.
Idealy you should brush the teeth once a day.
