...yes, I'm very glad about this topic, too.
I've never been one for increased showering... but I have to say I like the ritual aspect of cleaning yourself: I like to use scrubs (there are great scrubs from a company of "fresh handmade cosmetics", containing ground almond shells and cocoa butter), and I also like to take a ritual bath. Only when my body is covered in water I feel like I can gain weightlessness and distance from daily problems, it is high magic of renewal (and it's also very relaxing for the muscles, especially if you have to carry a toddler quite so often). I also like the effects you can reach with aroma therapy while taking a bath.
So... it would be nice to say goodbye to shampoo, but I couldn't do without at least a bath once a week; and a bath without getting my long hair wet is quite difficult... I'll think about it.
Does it necessarily have to be a brush, or is it possible to use a comb, too?
You don't need to avoid wetting your hair, just that some people find getting it wet too often encourages greasiness, at least in the beginning when you have just given up shampoo. As Heike says If you have a bath and don't want to get your hair soapy just wash your hair through with water in the bath and then keep it out of the way when using any soap or bath products.
A comb works too, but a brush has more surface area and maybe does a better job of spreading the grease from where its made near your scalp to the rest of your hair, and removing excess greasiness.