Here are some tips on polishing aluminum, chrome parts.
Tripoli
Brown (all-purpose cut and color) Used for basic clean up on minor scratches and light work, many times the first step to get an even finish and good color. Use a medium spiral sewn buff here, typically 3/8" sewing.
Chrome rouge
White (fine cut mostly color) Used in many applications as a final finish on very good quality metal or to color after Tripoli. Using a 3/8 spiral sewn buff is acceptable and for final application a loose buff is used.
Jewelers rouge
Pink (fine compound color only for mirror finish) Used to achieve a custom high quality "mirror" finish which is a final application after Tripoli or Chrome rouge. A loosely sewn buff is appropriate, but most often a loose buff is used with jewelers rouge.
Plated parts
Note: All compounds can cut through plating. You can do more damage than good polishing a thinly plated part. Also be careful polishing clear coat. Generally, you should remove all clear coat to do any polishing. Try not to mix aggressive compounds with color compounds on the same buff. If you need to use the same buff, clean it with a raking action. A file edge is best, but any heavy gauge metal, hard and straight will work.
Aluminum wheels
For polishing or cleaning an aluminum wheel or wheels first check for clear coat (this has to be removed to polish ex: Sanded off). The Polishing is usually a two step process. First using Tripoli and a buffing wheel remove scratches and blend out for the first step. Second using Jewelers rouge and a new buff, finish out the fine lines and blend. cleaning, polishing, and ection.