I reckon you could fashion your own scraper the stanley blade works fine but on the some angles it is pretty tricky it takes ages I usually sit out in the back yard as plastic goes every where if you have got something to keep you entertained it is easier a good beer supply helps too makes the time fly.
You can't really bugger anything I think if you get it to the nice original colour nice and early it makes it alot easier if your plastic is sun faded and crusty it will make it alot harder still can be done takes ages though.
