Given the number of questions and messages I've received in response to a forum post on removing anodized aluminum, I thought it might be useful to post a bit of a simplistic, step-by-step tutorial on restoring anodized aluminum trim.
So, here goes...wish me luck - I'm no teacher!

Before starting, you should be aware that once you remove the existing anodized coating and polish the trim, the trim will oxidize to a dull gray color again unless some sort final finishing treatment is added as a final step after polishing is complete. The oxidation may take weeks or months depending on the climate the truck is exposed to. To prevent this, either clear coat, clear powdercoat, Zoop seal, or brite-dip anodizing must be applied to make the shiny finish permanent.

Fig. 1

Fig. 2

2) Get yourself some Red-Devil Lye. A simpler way to remove the anodizing is to put 3 or 4 gallons of water in a 5-gallon bucket and carefully mix in a can of Red-Devil Lye. (One can of lye in 3 gallons of water will work if given time. 2 cans in 3 gallons is faster.) CAUTION: Wear proper gloves, and more importantly, a face shield. I'm not fooling around - BE CAREFUL - this solution will burn your skin and blind your eyes if it gets on you. Immerse the part you're working on in the bucket, or brush the solution on the part with a paint brush. After about 10 minutes or so, your part will be ruined. Actually, it's just temporarily ruined. It will be a lovely, dull, brownish-color and the anodizing will be gone. Within reason, the more concentrated the lye solution, the faster the dissolution will go. After the lye bath be sure to rinse the solution off the part(s) very well.
Here's the trim ring after it came out of the lye bath (Fig. 3).

Fig. 3

3) Next step is the time-consumer. You must pound out all the obvious dents and polish out all the large pits, scratches and gashes. I use a variety of sanding blocks, files, sand paper, and most effectively, fine and medium Scotch-Brite pads on a right-angle die grinder. Work to leave no rougher scratches than 800-grit paper would leave. Keep working until all the scratches are gone - but don't fool yourself: you won't be done yet. The first stage of buffing with Tripoli compound will reveal many more areas in need of attention. Trim piece after first round of sanding is shown at right (Fig. 4).

Fig. 4

4) Next go over the part with Tripoli compound on a buffing wheel and other mini-buffs, bobs, etc. to identify areas that still need to be sanded smooth, pits that need to be removed, dents that still need tapped out, etc. Fix those areas. Repeat polish with Tripoli until smooth. Keep repeating this cycle until the piece is as good as you can get it with Tripoli or you reach your level of satisfaction/end of your patience. Figs. 5 and 6 (at right) shows me working out areas of pitting with a Scotch-Brite pad after first round of Tripoli. This is also a really good time to get the trim piece hung up in the buffing wheel and sling it across the shop (or into your chest), creating a few more dents and gouges to back up and work out.

Fig. 5

Fig. 6

5) The last stage of buffing with White Rouge compound on a loose cotton wheel is the easiest and most rewarding if you've done the leg work to this point. The final product looks as shiny as chrome plate and is ready for your level of finishing - either put it on your truck and polish it every few months, or seal it with a specialized sealer (paint or Zoop seal, etc.), or get it clear powder coated, or (in my case) send it off to the local anodizer and have it bright-dip anodized for a permanent tough finish.

Hope this is helpful...let me know if you have questions.

PS: I didn't purchase pink shop towels. It's what you get if you wash your red ones with your white ones...

Fig. 7

Fig. 8