The best sand blaster is the one that someone else is running.
OKOKOK, I have one of the pressure feed ones from Harbour Freight, Central Pneumatic 40 pound.
I have never used it, I let some friends use it and they said it worked quite well.
The thing that has to be remembered when sandblastg is, sheet metal can badly warp due to the heat created from the media hitting the surface, it gets even hotter when the hopper starts to get empty and is running out of media, it is then like running an engine on too lean of a fuel condition and the execessive heat can do some real damage.
It is a dirty messy job, do not try blasting in Your garage/shop, no matter what kind of an enclosure You put around the blasting area, You will have dirt and dust all over everything.
It takes a very good compressor to keep up with any sort of a blaster.I have a dual stage rated at 17.4 cfm @ 100 PSI and it barely keeps up with one of those table top bead blasters.
Do`nt use too course of a media, it will leave the surface excessively rough, even frames, and then it is a lot of work trying to smooth that out with finer media.
The media can be used over up to three times, each time that it is recycled it gets a bit more duller, in , not taking off as much material, You will need to build an enclosure for this to trap it in and keep the execessive dirts and rocks out.
I had thought about using 1/4 inch OSB board and building an out doors enclosure with a lid on it, big enough for vehicle frames and hooking extension lights to it along with a couple of shop vacs for dust control and having a 3/4 inch OSB decking for a floor then I could retrieve the media and have a nice place to do that type of work in.
The lighting would have to be protected to keep the blasting from busting a light bulb, can You say spontaneous combustion from too much dust in the air, I think with two big shop vacs hooked to it that it should be relatively clean in there as far as dust, but, the lights would need to bne protected regardless.
When not in use I would build it with hardware so I could redily take it apart and stow it away to keep the weather from damaging it.
A good blasting hood would be a must, along with a good set of welding gloves to protect the hands, but, no matter what You use for clothing You are going to have that media under Your shirt and down Your neck. I hjave done some sand blasting for the DOT and it was a messy and dirty job.
There is the hand held gravity flow media blasters that works real well {even for electrical terminals} , does a nice job and are fairly inexpensive to operate. They do`nt take such a high output compressor either.