personally, i would get someone else to sandblast it ( i do over 2000 lbs of sand a year) it's dirty, hot, hard to do, and takes a lot of $$ invested to get a good job.
next, a good epoxy primer ( bars-rust 235 is what we use, from devo, industrial 2 part primer) then, seal any seams with automotive seam sealer. next, top coat with a good quality 2 part polyurethane paint. this will hold up well, and give you a lasting piece of equipment.
with all those square tubes, it will be a pain to sand blast, and paint. i would also drill a small drain hole at the bottom of any closed in tubes, and drill a 1/2" hole near the top, then spray in some automotive undercoating, to prevent rust from the inside.