We had a boat before the trailer. The best thing to clean the fibreglass and remove spider poop and black streaks is non-skid deck cleaner. It worked great on the boat and now on the tt. It doesn't take off the finish, leaves a little shine, and protects. The one we use is by Starbrite. Before that the stuff we used would remove streaks but also the finish.
6.5 lb Chihuahua (Bella)
2018 Rockwood Mini-lite 2109s
2016 Ford F150,FX4 Scab,5.0 L V8,