Step 1: Remove your brain.
This step is of great importance. If you can't physically remove your brain, 6-8 months of smoking pot heavily on a daily basis should do the trick.
Step 2: Use absolutely no heat to remove the vinyl decals.
See that heat gun, blow torch or even hair dryer over there? Just totally ignore it. You're gonna want to chip that vinyl off in timy little pieces, and make sure you leave ALL of the adhesive.
Step 3: If some of the vinyl is being stubborn, you should really get the scraper out and really get working at it. Metal is wicked hard. You aren't gonna hurt that, for sure.
Step.. what step were we on? I'm too lazy too look ALL the way up there
If you don't get all the way around to finishing taking the vinyl off, it's all good. I mean dinner might have been ready, that episode of Glee you've been dying to see might be on, there's a lot of stuff that can take a busy, hard working guy like yourself away from such a meaningless task.
Step next- Really screw everything up; break out the power tools.
You might be getting frustrated. maybe watching that saved by the bell re-run made you mad that you never got your own personal Kelly Kopowski. Power tools make stuff faster. Let's look through that shed, garage or closet and find something that'll really speed things up for you. Oh, you've got a power buffer? Detailers use power buffers! Detailers clean stuff up! You see where I'm going with this? Oh man, you're a damn genius. You just figured out how you're gonna save those greenbacks!
There's a trick to this though, so pay attention! You back with me? Cool. I need you to keep that buffer in one spot until ALL of the adhesive is gone. don't worry about the paint, metal is hard, remember? Just keep it RIGHT where it is. If anything goes wrong, people always say "that'll buff out" so I'm sure we can fix it.
Step Oh F*#%&)K
Oh man... I forgot to mention. Metal's wicked hard, but paint... paint's kinda not hard. all that buffing that you did on the adhesive? Well, that area's looking GOOD, but the adhesive kinda acts like a sandblast mask, so you might see some "ghosting" in the area around the letters. It's cool, people pay big money for polished aluminum.
If you got this far, CONGRATULATIONS! You only got this far on one spot? It's cool. Ship it on over to the sign guys. That compound in the adhesive? Leave it. They can go right over that.
I know you're smart enough to realize the sarcasm in all of this. This was a perfect case of "Penny wise, Pound foolish;" When we quoted this trailer lettering job, we figured on 3 hours for removal. This guy has at least triple that in getting this far. Our shop rate for 1 guy is $75 an hour. We've got 7 hours into fixing this mess. so to save $225, he's now $525 and at least 12 hours of his time. Please, let the professionals, with the proper tools and experience handle your next job.