while doing some wiring I did it to a part of one of my flares. seems like it works very well.
i guess you can melt and warp the fenders if you stay on one spot for awhile, but if your not stupid, they'll come out ok.
it doesnt make them brittle or leave them "burnt".
I dont know how long it lasts tho since i took them off awhile later.
You can use a heat gun on the jeep or use a handheld propane torch off the jeep, either work very well. It lasts about 2-3 years, about the same time it takes them to turn the first time
You could probably use an oxy torch too off the jeep but I think that might be a tad hot.
I might take one of my flare extensions that I took off and throw it in the oven at various temperatures and see if that does it, nah, that does not make any sense, the full flare would not fit in there anyway even if it did work plus the wife gets a bit touchy when she sees kitchen stuff headed for the jeep or the workbench or stuff starts coming up into the kitchen off the jeeps and there is any combination of words that include dirty grease.... it was easier to go buy my own baster for topping off the batteries than 'The LOOK' of borrowing it....
Tried using a propane torch on part of my front flare tonight and i have to say it worked great!! It goes right back to black and doesnt rub off or anything. I'm planning on doing my whole jeep with this method as soon as i pick up a heat gun cause the propane torch flames out if you hold it upside down and its a pain. I feel a heat gun would be perfect for this job. I'll try to post some pics up of the one spot i did with the torch in comparison with the rest of it and you can see for yourself.
Looks pretty cool, hope it works out for you. post your results when your done im interested. The only thing i could see as a concern is it leaving lines or streaks from not getting it perfectly even. I would like to see some pics of it in the sun light.