Pigeon & Nubby sell sets of 3 tooth brushes, the first stage is a rubber "brush" and the great thing is they have a round thingy that prevents LO from shoving it right down their throats, so they can start off by chewing on the brush and the rubber on it "brushes" the teeth.
I also had one of those finger brushes, but nether boy enjoyed my finger in their mouth, so I gave up on that one.
I started them on the first t/brush while they were still toothless wonders, so they could get used to brushing twice a day.
As Julz said, no need for toothpaste at first, but I started adding a tiny drop of Aquafresh Milk teeth toothpaste when they started losing interest with brushing (sort of a bribe)