well, all that air dried enamel stuff is pretty much the same cr@p... you wont find anything decent at the depo, chain stores.. seems a waste to blast it for that.. but it's your rig, whatever avenue you take... I was talking more like 125 for sprayable primer, and the same for paint...
I'm sure you'll have a chorus of eastwood chassis saver, POR15, etc like that at this point.. but air=dried, is air-dried....all rattlecan primers are cr@p, so I'm not gonna pick one...
but sure, get something that describes itself as a self-etching primer, coat of that, than brush on the rusto..
you could spend a bit more and go to a west marine for some moeller ryoken green in spraybomb... runs about 10 a can... 3, 4 cans would get a decent coat on that...