Remove any anti-slip strips with a cleaner and degreaser. Wash the tub with an abrasive cleanser. Scrub the tub with an abrasive pad and Lime-A-Way.
Sand the tub with 400-600 grit wet sandpaper. There are a couple of reasons for this:
When you're sanding, it's best to use wet sandpaper so the grit can be rinsed away while you're working.
Mix the epoxy and paint it on with a brush and roller.
Note: Small bubbles will appear on the surface as you paint, but as it dries its self-leveling properties will eliminate the bubbles.