I learned a lot of polishing tricks from the guys out at Little Sister's Truckwash in Barstow. If your tanks are sandblasted, and I'll assume they are if it's been over 3 months since they were polished, a best result would be wetsanding them with 200 or 400 grit paper - use fuel instead of water. If you have a vibrating sander, it'll make it a LOT easier.
Or, if you're near a Blue Beacon that still does acid whitening (many have stopped due to EPA regs), it will open up the metal for polishing, provided it's not too rough.
Get a good grinder/polisher. DeWalt seems to hold up well. You want 3000-4000 RPM tops, a lot are 10,000 RPM, and other than destroying your wheel, it'll burn the aluminum. I always only used the yellow wheels with green rouge (from TA truckstops). You can use the white wheel and white compound for a final buff, but if you're driving the truck, it's really not worth it - things dull entirely too quickly.
You'll use the edge, put the rouge to it so that it melts onto the wheel, then start at the bottom, moving up in back and forth strokes. You'll have to keep putting the rouge on as needed. That puts the "cut" into it. Then you'll do the same thing, starting at the top, working your way down.
First time, tanks will take about 2-3 hours to start looking decent. As for the bullbar, I don't know if I'd attempt it. Stuff out front gets sandblasted so bad, that it would take a LOT of sanding and even grinding to get it ready to buff.
