Hi.
A thread I responded to had asked the question after using a product that Bled and created a FUBAR! The biggest problem here is not everyone can get or have access to a Vacuum Forming rig.( this was a Good Suggestion though).
Many times I had found myself with the same dilemna while rebuilding odd Glue Bombs! Cars were easy because Just flat Evergreen Sheet Clear in .101 worked great. Now Planes,Well..... Let's just say I had a few on the "Shelf of Doom" Someone asked if I still Had the original."Sure", I said.
Well they introduced me to the really fine sandpapers then Polishing compound and a Baby's toothbrush. This worked pretty good. Still didn't restore that pristine clarity though. Close but no Cigar! Then a wise woman called Grandma came up with this. "Have you gotten some of that Pepsodent white Toothpaste"
This is important folks.Toothpaste, NOT Gel! Well, this is after a cleaning and polishing compound for Teeth! I listened to this wise lady. She said use it like rubbing compound and with a very soft cloth, rub till it gets like new!
She was so right. So, listen to Grandma after you've restored the part as well as possible with 12000 grit and then Rubbing Compound. Get the Toothpaste, what a difference! It's hard to find nowadays but you can still find it. If not, use Tooth-Paste for dentures, It works too!
Yes, in closing It's labor intensive, But, what if you cannot get replacement parts.? Make this your go to, in this situation.