Very soft work with a q-tip and water first to get the dirt off because you don't want to abraid the surface by rubbing around dirt. Then once clean, take a very fine cutting polish and a q-tip. If you work at it very delicately you can get a lot of the discoloration out. And keep switching out q-tips for clean ones. You are trying to remove the embedded dirt and grime and don't really want to keep moving it around. Once you go over a small area, flip it over to the clean side, then do some then toss and grab a new one. However, you need to guage if the decal can take it or not. Many can, some can't. You will know within the first few minutes if there is hope. I have had a lot of good lucky with most, but some are just too dry and about to flake off and won't take any work on them.
Hmm, I need some opinions here. Since the white
rear fender has all of that nasty safety tape on them( bad idea), and i can’t find my heat gun( hair dryer), was considering putting some stainless 60 Traveller fenders on. They have chrome braces also. Although not original, could look pretty sweet.