What kind of dirt do you have on the dash? Mine is just dust, I used the Flash DustMaster and the other brand with a green handle. Now I just use Flash all purpose wipes, which leaves a pleseant lemon smell. There is no need to use special products for Dashboard (or the rest of the interior, TBH). I use the wipe (and the dustmaster) on my plasma tv and moulded polycarbonate speakers at home and there isn't a single scratch mark. Works very well and not expensive. It wipes off light finger marks very well.
But if you have heavier dirt, damp kitchen towel to soften and absorb first. Oily stuff, you would want tissue from McD as they suck grease like nothing else!