SEALER , A wash job is in order , get the dirt off .Degrease the thing to remove all Oils, silicon based products, and ammonia based stuff. Tree sap and the acid rain marks. That's the hardest part is to get the surface clean. Wipe sealer on , after it dries wipe off. It gives a better shine if you use a soft cotton towel or Buff off with one of our Drum type polishers. Wash with the hottest water you can stand with Dawn, we sale a Landing Gear DEGREASER < 1 gal. Makes 5 gal. This removes all. Used by US AIRFORCE, BOEING, to name a few. We always wash Airstreams and Aircraft with this before we polish. You might note we have a interior cleaner that shall restore the old Airstream Splattered paint to look new super stuff, if they use this in the Aviation market how can it be bad on a Airstream ?

JW