Yeah - we brush our teeth with Jenna, and she is also pretty familiar with the toothbrush as she quite often walks around the house with it!
She has one in each bathroom, but we are pretty laid back about it. If she wants to chew on our toothbrush, we let her do that too.
I sometimes brush her teeth (she still only has 2!) and she will let me do it for a few seconds.
When I am brushing my teeth, she will put her brush in her mouth and swing her wrist around like shes copying.
I agree with the whole fun thing making it easier.