i use a propane torch quite often to heat up parts that im going to TIG. especially when im welding thick to thin or a old part when welding a new part to it like a replacement tab for a nerf bar or something like that.
Another good cleaner for aluminum is aluminum brite an acid based cleaner.
good to know. acetone also works well. i wipe down the filler rod before i weld.
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CB8QFjAA&url=http%3A%2F%2Fwww.homedepot.com%2Fp%2FKlean-Strip-1-gal-KS-3-Premium-Stripper-GKS3%2F100144685&ei=wFcdVYTxJYzboASW1oGIDw&usg=AFQjCNHhpgR-mPj-eAAPS_wR4hxQrt5dkQ&sig2=eJnc3V-tKlaErec7_lB1yQ&bvm=bv.89947451,d.cGU&cad=rja is a damn good price for a srtipper
Acetone or thinner is great for wiping down for oils where as aluminum brite will strip paints as well as clean it.
i tried the aircraft stripper first an it did not even bubble. this was some tough paint, till i used the clean strip !