I don't know of anything that works for more than a few days. I've used alcohol or amonia (sparingly) to clean off accumulated wax build-up and then re-polished with a good wax, but the shine doesn't last long. That was on a 9 year old trailer.
The graphics on my current rig are almost 5 years old and still look great, so haven't experimented lately.
Go to Griots garage and order you an orbital buffer.? Any orbital sander won't work unless it has a dial to set the speed lower so you can controll the speed.? They also sell foam buffing pads.? This combination will not burn your stickers or paint/gell coat.? A regular buffer that just spins is more likely to burn the paint and is harder in my opinion to use.? The random buffer is a snap.
You can try Griots garage buffing solutions but they are for very light swirls and are no match for deep oxidation.? I would go to a professional grade liquid compound.? They are usually a three step process and in your case, start with the lightest compound and see if it is enough.? I just re-did a race car and used the harshest compound to take a layer of paint off as it was very chalky.? I went over the racing vinal stickers and the car looked great.? I even used it on the plastic tail light lenses and they looked almost new. It took all the scratches and swirls off and the stickers looked great.? I went through the next two steps with finer grit and then did a final polish with a good quality wax.? I know the directions say to change foam pads with each grit but don't bother.? Most if not all the grit gets slung off and I and others that have taught me to do this said the same thing.? Don't waist the pads.? If you are doing a show car then by all means change the pads but for a buff job on a older MH to restore the shine let her rip.?
Look for 3M products but any will do.? I think my harshest compound started with a 800 grit and went up from there.? The Griots garage compounds may be great for the last step or two.? Start off in a inconspicous place to test how things will go but I bet you will be amazed at how easy and fast it will go.? The vinal will hold up fine with this process and it will strip all the old wax off.? Be sure to put your final was coat back on as this stuff has no wax in it.
Meguires tech protect.
Best stuff I ever used on my old rig.
I wash, dry, then get a rag and wipe the whole moho with the stuff.
She will shine like new. Water will bead off like you have 5 coats of wax.
Works great on your interior plastic and fantastic on tires too.