worked great on my plastics they were very dirty from sitting outside for a few years also scraped them with a razor blade to take most of the grime off then used steel wool to finish them off.
SOS pads are a very course steel wool impregnated with soap.
you could start with that, but a fine steel wool will give a better finish for the final lap
I did this on my old blaster, it works well but i had white plastics and therefore was kinda pointless...plus the little lips at the ends make it really difficult to get it done all around...it's generally pretty time consuming, but easy and cheap
I recently used some Shower cleaner and a scotch brite pad/sponge on a set of white plastics. It took the years of ground in grime right out of them. Then I used the steel wool, mop and glo so on and so forth.
I did this on my gas tank cover and it worked fairly well. I tried to finish it up with steel wool and sand paper, which were able to get it smoother, but they stained the white plastic so I'll finish it off with a heat gun when I have time.