I polished mine about a year ago, and this is what I did:
I just removed that silver trim around the guages to get at the clear plastic. I then used Meguiar's Mirror Glaze Professional No. 17 Clear Plastic cleaner followed by No. 10 of the same brand. It worked pretty well, but did not get out all of the big scratches. Here is what the back of the bottle says:
Use Mirror Glaze Clear Plastic Cleaner (No.17) to remove fine hairline scratches from all types of clear plastics.
IMPORTANT: To restore optic clarity and lasting protection, follow with an application of (No. 10) Polish. For major repairs, use Mirror Glaze Defect Removal System. Use (No. 18) Cleaner/Polish for regular maintenance.
From: Aaron Smith