I am looking into painting my aluminum boat. However, there was a question I have about some stuff on the bottom. Its a gamefisher boat, and it has this hard (almost like bedliner) black stuff on the bottom, and its rough. Could I sand that smooth to paint it? Or is there a reason why it is rough like that? It seems like without that, there would be less resistance. I am new to all this, so sorry if I look dumb.. 