Clear coatings on fiberglass exterior doors take a huge beating - especially clear coatings behind a storm door. I have seen traditional clear finishes and plastic parts on doors melt from the sun's heat. Acid rain, ultraviolet light, and other atmospheric pollutants simply erode clear finishes on fiberglass doors, polished brass and many other outdoor items. The key to minimizing restoration work lies in keeping up with the coatings.
Flat interior paint has always been tricky to clean. Newer washable flat paints make cleaning a cinch, and hide nicks and dings. Paint with 100% acrylic resin will do the best job.
When painting metal, read the label of the paints first! Paint metal to avoid rust with primer and paint with rust inhibitor and be sure to prep the surface well. Check to be sure the paints and primers are compatible as rust preventive agents as well.
Paint that prevents rust on steel must have a rust inhibitor. The primer should be oil based and contain rust preventive inhibitors. Be sure to check the label and use this list of companies as a guide.
The right paint and primer can deter rust. Avoid the job of rust removal by using primer and paints with rust inhibitor. Rust preventive primer contains rust inhibitors - check the labels. Oil based paint makes the best primer to serve as a rust corrosion inhibitor.
Urethane or varnish? Oil based paint of urethanes or water based finishes for your urethane coating? Clear coatings are complex. Which is best? Tips for choosing the right urethane paints for the job are explained here.
Urethane needs special handling. A urethane coating of an oil based paint vs. water based finishes requires different prep and offers different results. Do not shake urethanes, be sure to provide proper prep of the surface and watch the timing of additional clear coatings. Urethane paints will provide a superb urethane surface, but you must choose the proper urethane paint for the job and apply them per the label instructions.
Drain cleaners are not all the same. Some liquid drain cleaning products should only be used by professionals as they are extremely dangerous. The off-the-shelf drain cleaners found in grocery stores rarely harm pipes but they can harm you if you are not careful.