You can add a painted finish to your old shower panels if you thoroughly prepare them for adhesion. Because they are slick and waterproof, shower panels don't hold paint well. To ensure a lasting finish that won't strip away, condition the panels to improve adhesion. Opt for one of two paints specifically formulated to withstand water exposure, or failure is bound to result.
Nothing will bond to shower panels marred with dirt and soap scum. Before doing anything else, scrub the panels with a degreasing cleanser. Ordinary soap may not loosen stubborn residues. For a thorough cleaning, use a heavy-duty trisodium phosphate-based cleanser.
Slick shower panels can't hold a painted finish. To increase the panels' adhesive qualities, abrade them by scouring each one with 100-grit sandpaper. Rougher surfaces hold primer and paint much better than smooth ones. Don't leave any part of the shower panel unsanded, or the finish may begin to peel up in that area.
Even clean, abraded shower panels will reject paint unless they're treated with an appropriate bonding primer. Though you may use a latex primer, for optimum durability, opt for an enduring, flexible acrylic primer. Never paint directly over bare shower panels, or peeling will eventually follow.
Plain water-based latex paint is fine for most interior surfaces within the home; however, it won't last more than a few months inside a shower. For long-term durability, apply either a two-part epoxy paint or acrylic enamel.
Professionals generate slick, flawless finishes by applying primer and paint to shower panels using a gas- or electric-powered spray rig. If you have experience operating these devices, do the same. If you do not have this critical experience, don't use a spray rig or you'll likely end up with severe sagging. To create an attractive, professional-looking finish, apply the primer and paint using a roller equipped with a foam roller cover. Eliminate roller marks by lightly brushing the wet finish using a wide polyester brush. Don't use synthetic nylon brushes, which may leave ugly stroke marks in the finish.