It is also not a good idea to sand blast it if you can get it dipped n stripped. If you do have it blasted spend the time with a pick and shop vac and maybe some high pressure air to blow out the sand that has gotten blasted into the crevices. If you leave any in there the por will coat it but it will leave bare metal under there where moisture can get trapped and rust out over time.
As far as mixing and matching primers and finishes thats not a good idea, the manufacturers spend alot of time, devleopment and testing to make their stuff work together, anytime you mix brands all bets are off as to durability.
If you have the resources to put it in a closed room, sealed from the outside with plastic drop cloths taped to the floor and ceiling do it, also put an ELECTRIC heater [not kero or propane] in the room a few hours ahead of time to dry it out. Kero and propane byproducts are moisture which is why the electric will work better. If possible try to hang the frame from all 4 corners. Local shop by me uses a couple of old gym sets with casters welded on to the legs to hang stuff from. When not in use they roll them into a corner out of the way. Works pretty well, he got the gym sets from yard sales for like $10 ea and they use them to hang all kinds of parts for painting.