I'm getting ready to do the inside of my tub with monstaliner and have seen some pics with it done to the outside as well. I wanna do the outside of mine in black. Judging by the pics i've seen it gives it a pretty unique look. For anybody that has done it to the exterior what's in the prep? I'm assuming sanding but do you have to get rid of the paint, just rough it up, is primer needed, etc?? Any info is appreciated, thanks guys.