Replacing a bathtub or shower can get expensive with all the disposal fees and the labor. An easier and cheaper option is to refinish your bathtub on your own. To refinish the tub you will need to use gel coat, which is a poly ester resin that is tinted to match any color. Gel coat has wax in it which gives the surface a nice shiny finish. Gel coat is very thick compared to other paints and is sprayed using a gun just for gel coat. A gel coat gun can be purchased at your local marine supply store.
Sand the entire surface that is getting refinished using a fine-grit sandpaper. A palm sander can speed the process. Make sure the surface is scuffed thoroughly. This is important for the bonding process.
Wipe the entire tub out with a clean rag and acetone. Remove any grease or dust that is on the surface. Grease can cause the gel coat not to bond properly, and the dust will leave a rough finish if painted over.
Tape off the entire area around the tub and any sink or toilet around the tub. Cover the walls and the floors using plastic. This will prevent any over spray from getting in unwanted areas.
Put on your respirator, and spray the first coat of gel coat on the tub. The first coat should be a thick mist. Do not try and make the gel coat cover in the first coat; this could cause runs in the paint. Let the first coat get tacky, and apply the second coat. The second coat can be a little heavier and should cover the entire surface. If the second coat is still not covering, you can wait until it gets tacky and spray a final light coat on as needed. Let this cure until it is hard and cool to the touch.
Remove all of the tape, and clean any residue left by the tape using a rag damp with acetone. Also clean the gel coat gun using acetone so the gel coat does not harden on the tip.
Always wear a respirator when working with fiberglass.