sand blaster

First, you need a pressure blaster, not a siphon feed type, if you are doing a lot of area. Plus pressure type uses less CFM.

Then you need a lot of CFM or else a tiny nozzle. Tiny nozzles will keep the pressure up on a small compressor to clean rust pits quicker. Lower pressures will do fine for paint. Small nozzles do get plugged easy, so use a strainer or screen when filling the tank.

If you are trying to clean out rust pitted metal really clean, a finer grit of sand is best, coarser is much quicker on multiple layers of paint.

If you can't save the used sand like in a cabinet, then you can't afford the fancy abrasives. White quartz in fine grit is good & sharp for pits, but is the most expensive "sand". There are cheaper grades of sand that are tan. A friend of mine who has blasted for years, just tried "sand box sand" from Home depot or walmart and said it's cheaper than the low grade blasting sand, and works good if you strain it first.

There's also "black beauty" a by-product of steel making, cheaper but needs to be strained real good and is better used on paint than rust.

A siphon feed might be ok for small area that's not rusty, but they do waste sand & air compared to pressure blasters. One last thing, all undercoat, grease & sealers need to be scraped off first to save a lot of time & sand.

Messy job no matter how you do it....but someone has to.....