I had one old dog that liked the electric toothbrush. (I used my wife's brush, naturally. ;-) )
I have a friend whose dog sits by the sink every morning while she brushes her teeth and then gets hers done. But most of my dogs are a nightmare with a toothbrush and (any kind of) toothpaste. A good big frozen raw cow leg bone works better - if you can handle the messes.
If your noticing a build up already it is a wise idea to try and prevent any further buildup. You can use a regular toothbrush and pet toothpaste. Don't use the human stuff as it foams up and they can't spit it out. I do use a electric toothbrush also as I feel it does a better job.
If your dog chews on anything then great, get him lots of chew toys and bones to help prevent the buildup. There are dental chews out there that are impregnated with a product to help cut down on the bacteria in the mouth that causes the tarter buildup. There is also a liquid called Aquadent that you can add to the water to help.
I asked my vet about cleaning teeth and he said to just buy them a pigs knuckle from the farm store. I buy the kind that do not have any of the thinner leg bone attached because my dogs could chew that up pretty quickly and I was worried about slivers. They gnaw on the knuckles for two or three days before they are gone and it keeps their teeth nice and clean. I buy them one every couple of months when I pick up feed. Works for my dogs and they love it.