All the one's I've done in the past I've had the tires off (value stems and tire beads create a lot of work arounds that end up being more trouble than leaving the tires/valve stems on...not impossible, but aggravating. So you think you want to tackle some expensive Viper rims eh.. OK then.
I'd practice on a piece of aluminium just to see what the process is like...get a piece of scrap such as an aluminium cookie sheet or something you can polish up. Grab your neighbors diamondback aluminium runningboards or tool box for starters!!
1. Dismount and remove tire/valve stem/center cap.
2. Remove clear coat (I prefer to use progressively finer grit wet/dry sand paper...600/800 to start...moving up to 1500... finishing with 2000). Don't skimp on the sand paper. Use it freely and keep the piece you are using sharp/wet/clean. Use a soapy mix. I do not like to use chemical removers since I have had some products etch into the aluminium and I had to spend considerable time sanding out the discoloration (especially in tight spaces).
3. Once the finish is free from clear coat and any other imperfections (curb rash can be sanded out as well), the fun part starts.
4. I use a 6" D/A air sander with a wool bonnet that simply stretches via elastic over the sanding pad. I'd probably get one of those Mother's Balls too for use in the tighter areas (or something similar...the more tools you can use for the job vice hand/arm power the better).
5. Put some Mothers Mag/Aluminium polish on the pad (about 2x what you'd put on your toothbrush). You can do this all by hand with a cotton cloth too, but after one rim you will be tired. At any rate, start the polishing process on one of the larger spokes. You will notice the residue from the polish turning a dark black the longer you work the area. This is the reaction from the polish, heat, and the raw aluminium and is a good thing. This is not an indication to put more polish on the rim!! Less is better and let the polish/residue do its work. From time to time, wipe the area with a clean cotton cloth and you will see a chrome-like appearance coming from the polished area. If you did the prior sanding work properly, this will be scratch and defect free and only get better the more you polish. If there are fine scratches, hit the 2000 grit wet/dry and sand again until the imperfections are removed.
6. Polished alumimium looks a bit different than clear coated or chrome so don't be shocked by the contrast (take before/after pics). Sort of deeper and softer vice the bright flashy look.
7. Now, after this is all done, your rims will look wonderful, but any thing that gets on the rims will quickly tarnish the finish (remember, you have raw polished aluminium vs. the elements). A good wax/polish can help, but every few weeks or so, take a clean rag with some Mothers on it and work the rims. You wil once again get the black residue each and every time you do this. This is the indication that the polish is working.
8. The clear coat and chrome fans will jump in at this point since that is the major drawback from this process. Once you go clearless/chromeless, you have to polish/maintain regularly...but you will have the flexibility to maintain your rims better over the years of ownership. Oh yea, speaking of that, resale will probably be less if you do this to your rims...if the buyer has any wheel knowledge.
9. Time frame...probably take one hour per wheel with the tire/valve stem off.