I used Rustoleum spray bedliner on my hardtop and it worked out great! I didn't even have to sand it, but I would probably recommend it. None of it is peeling or chipping or anything, but sanding and giving it a better grip couldn't hurt.
I used basic blue painter's tape and some newspaper. I wasn't able to remove it myself, so I painted it while it was still on the Jeep. Mask off hardtop windows, rear windshield, and the vents. I just masked off the edge where it meets my Jeep, the edge of the doors, and the windshield, just in case.
It turned out good, I'd highly recommend it. I only used 2 cans, if I remember correctly, and that's with two coats. It's roughly one total coat per can. Good luck, and post pictures!