I don't want to hide imperfections. I want a really rough surface texture.
Hence the brush...

Using a brush also removes the need for serious ventilation masks.

I do not want to remove the old paint, as I said.
I could consider sanding it lightly, but I'm not sure what that would do to the stickers (or decals or whatever you call them).

Oh, and I'm looking to keep the costs down to a minimum.
$20-$30 total.