Ahh sand blasting... you can spend ALOT of money on sandblasting equipment.
Im no expert on this by any means, but dont forget to get a water seperator for your air lines. water + sand = bad news. Also, you MIGHT want to get a water cooler to cool the air as well, as the air can get quite hot.
Also be sure that you are ready to paint with in an hour or so after sand blasting or your wasting your time. I have watched stuff rust right in front of me. So keep that in mind. As soon as your done blasting, dust it off with plain air, and start painting. Be sure to use a high quality primer.
Also, depending on what you use, depends on how rough the surface will be. Glass bead is said to be decent, however I have nexr used it, It IS expensive. Pool sand is actually pretty good for MOST projects and doesnt pit the metal terribly, There is this other stuff thats called black beauty that cuts extremely fast, but when you prefer smoothness over speed, its not the greatest, but it cleans the best.