Hi, I've searched the site for an answer but cannot find anything...must be using the wrong words or lost in translation!
I've got 2 sets of the original Gtr/C10 panniers and was hoping to make a good pair from them. But. I just cannot get them to anything like acceptable finish. All the cases have usual scratches and scuffs from years of being thrown around in storage, and some deeper ones from going down the road 
I've tried every sort of polish known to Man, scotchpads, wire wool, heatgun, gas lamp...and nothing has worked. The best finish I've got so far is a sort of shiny grey sheen, but still look terrible!
I'm thinking of flatting down the grained finish a little, then spraying paint or something like Raptor bed liner, has anyone found the answer? 

If you want a smooth finish, prepare for many hours of sanding followed by a layer of plastic filler, more sanding, more filler, (repeat until surface is perfect) and eventually primer and paint. Then prepare to swear like a trooper the first time you chip the paint. 
Otherwise, some have painted theirs with bed liner/textured paint and others just paint them matt black.
Personally, I have a set of 1986 "smooth from the factory" panniers and I have just covered them with stickers. 

Stickers it is then!
I've tried all the stuff I've used for many years of vehicle repairs...no joy!
I have 2 pairs of panniers so I'm taking the worse pair and experimenting...watch this space....  

Ive had good luck with this .

https://www.amazon.com/Mothers-06141-Back-Black-Cleaner/dp/B00GZLMEDO/ref=asc_df_B00GZLMEDO/?tag=hyprod-20&linkCode=df0&hvadid=312192374842&hvpos=&hvnetw=g&hvrand=10858590364800580623&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9027419&hvtargid=pla-450199862845&psc=1


And have used this on my rear fender which was pretty grey and bad .

https://www.eastwood.com/ew-plastic-resurfacer-matte-black-aerosol.html

Another option is to paint the outside shields with spray on dura-liner paint which goes on with a coarser pebbled finish than the OEM finish and might hide a lot of the current defacement.