I wouldn't waste my time painting it with the dash in place. You need a wet coat for both coverage and adhesion. If you just spray "dust" coats, you'd be able to wipe most of it off for lack of adhesion. Its the suede additive in the paint that gives the texture, not light dustings. But having said that the proper paint and additive is hard to come by and there are other techniques that seem to work. I just wouldn't bother without removing the dash.