Polishing a dustcover
Although I have used the first method for many years with great success, but have NOT used the second method, I must caution you to proceed at your own risk with either set of directions. I will not be held responsible should you fail to get the desired result, nor if you cause additional damage to your cover. If you don't feel confident in your skills, do NOT attempt either procedure!)
Tape over any emblems or badges on the cover, as the lettering will come off during some of these processes!
1st...0000 steel wool over the worst scratches (the whole cover if it's THAT bad).
2nd, under running water, enough Comet to be almost a paste and a sponge over the whole thing.
3rd, Automotive (DuPont) rubbing compound (preferably done on a damp electric buffing wheel.This step will take about 15 minutes, give or take (when done by hand), depending on how much elbow grease you use. You can proceed to the next step when the cover is once again, transparent and somewhat shiny. Wipe it off with a very soft cotton rag.
4th is Automotive (DuPont) polishing compound, again best with a buffing wheel... This step will also take about 15 minutes (when done by hand), and the cover should be totally transparent, pretty much scratch-free, and very shiny. Only then should you wipe clean with another soft, clean cotton cloth.
5th is Meguiars brand Automotive cleaning wax (It's a paste wax & slight compound in a red can). That can be applied by hand with the sponge that comes with it. I do the top AND the 4 sides with it. Rub it in good,(about 5 minutes) then clean off with yet ANOTHER clean, soft rag!! Keep in mind that the more elbow grease that you use in each step, the better the job will come out. You'll never get out the deeper scratches, but depending on how bad it was when you started, it should improve immensely! I've had covers that had become translucent that I was able to bring back to transparent...and shiny, too.
The 6th and last step I recommend is to spray the inside with Windex, AND a shot or two of liquid spraywax, letting the two liquids mix together (Pledge or equivelent), use another rag to wipe it all up. Do the same for the outside of the cover when the inside is dry. The reason for the both liquids is that spray wax by itself streaks, and Windex by itself scratches. Put the two together, though, and you get just the positives!
By this time, you should have a shiny like-new cover that should slide right out of your hands!!! This last step is one that should be done on a regular basis in order to keep that wonderful shine. Never use a dry rag to wipe it off...that's what causes all of those scratches and loss of shine in the first place!
The following was sent to me my an experienced aircraft plastics refinisher. It will require more time and materials, but if you are very handy, it should yield better results than my more simple method shown above. As I said above, I have NOT tried this method, proceed at your own risk.
Second, always use some sort of foam pad or 'soft block' made of foam to support your sandpaper; never sand with the abrasive in your bare hand. Doing so may cause depressions and optically disturbed, 'lensatic' spots which detract from the job.
Third, select the right compound for the job. 'Imperial Microfinishing Liquid Compound' from 3M is an excellent all-purpose first cut compound havig an extended aggressive cut and fairly fine finish. You can follow this up with 3M 'Finesse-IT II Finishing Material', a white aluminum oxide based polish supplied in clear plastic bottles or 3M 'Perfect-It' machine glaze, a white aluminum oxide based polish supplied in black plastic containers. Use a wool bonnet on your buffer for the rough cut and switch to a foam pad for the finish cut. This will eliminate swirl marks. Meguiars makes excellent products, I simply prefer 3M. Meguiars #3 machine glaze would be an excellent alternate for the fine cut polish. I would avoid using any product which contains wax or silicones until you get all the scratches out. Waxes can fill the scratches thus temporarily concealing them.
Always remember that it is easier and faster to remove defects with the rougher materials; don't stop sanding until all the scratches are gone. Don't stop with the rough cut polish until all the sanding scratches are gone.You don't want to try to polish sanding scratches with your final cut polish because its inefficient.With each successive step you goal is to remove the traces left by the last step.
After you have mastered sanding with wet-or-dry paper, you can switch to dry paper for the random-orbit or DA sander. This is available only from 3M. It comes in grits from P600 to P1600. P1000 is a good all-round paper and is the only one I use. Swiching to power sanding as above will reduce your sanding time by about 75 to 90 percent. Using the above methods I can completely refinish a cover in about one to two hours from start to finish, regardless of condition.
Whatever methods you use, be conscious of stray dirt and dust, especially during sanding. Rinse often if wet sanding (a running stream of water is best). Wipe often with a clean rag if dry sanding. A compressed air blower helps too. Never allow your buffing pad to touch the floor as it will pick up dirt which may leave scratches.
All of the above materials are available at you local auto paint and body supply.
So your shopping list will be:
First cut paper, wet-or dry (P600)