Using the brush and just water is the first step in getting the dog used to having teeth brushed; so it can't hurt. You can then see if you are making progress, or need to step up a bit.

A slice of raw sweet potato also helps keep teeth clean.

I know you can't use human toothpaste, it must be toothpaste made specifically for dogs. And it comes in flavors - beef, salmon, etc. Other than that, I don't know much about it.