what primer to use?

[Ochre]

Ok, so the blazer I recently purchased has some, uh, body issues to say the least...its a MN truck what can I say...

My question regards the bedsides - thanks to environment and no doubt a bit of help from the road salt here, the bedsides are peppered in nasty little bubbles anywhere from 1/16" to 3/8" in diameter, some of which have "popped" and there is visible rust.

That said, there's also rust in the "regular" areas of the truck, and I'm not going to paint the truck until the rockers, rocker boxes, WS frame etc are all repaired. However, in the meantime, I'd like to stop these spots on the bedsides so that bedside repair and replacement pieces can be kept to a minimum. I don't have the luxury of a garage/barn to keep it in (permanently) so for now its only going to be wheeled into the garage when I can spend time working on it, and wheeled back outside when I'm done.

I was thinking that the thing to do would be to sand off the paint on the bedsides, grind out any spots where rust has dug into the surface and possibly finish them out by throwing a weld in the divit left by grinding out any rust and going over with a flap disk...not bothering to bondo or anything, at least for the time being. Now comes the hard part - what should I spray this with, knowing full well that I probably won't get around to actually painting the truck until late next summer, or possibly even later? The truck won't be on the roads this winter, so road salt isn't a concern, but snow & spring rain definitely are. Being able to clean off (reasonably) easy for when I get to the point where I can sand down to bare metal and finish out, prime & paint.

Would you guys recommend weld-thru? Primer-sealer? Something else?

I'm not really well-versed in bodywork, though I'm eager to learn. I have a cheapo home-depot HVLP gun for spraying paint if that helps. I don't *really* care how the finish looks once sprayed (primer jobs usually look like crap anyways) as long as it keeps rust at bay.

Thanks for the help