elbow grease...
start off with a carpet knife blade and gentle scrape at the scrathes and try to flat them out a little
Then get some water paper, start with around 180 grit, sand and sand and sand, then move to 220, 320 then 400, 600, 800, 1200 and finish off with 2200. change your water with each grit change
Then get yourself a heat gun and blow the plastics until it gets a wet look, do not hold too long in one spot or you will melt it! allow to cool and wipe on some furniture polish.
it takes time but its wort it