Mark,
If you grind or blast your pieces to bright metal, then spray on something out of a aerosol can, technically, you will have to do the whole process again the get rid of the spray can paint.
The bond for any finish coat is only as good as the coating under it. Spray can paint wouldn't be compatible with anything truly automotive, and might cause nasty problems when you tried to over coat it with something else.
The 2k primers are impermeable when dry so your metal is safe from the elements....spray can stuff isn't and you would soon find rust appearing.
Painting procedures can be daunting but just remember that bare metal must be sealed from the environment, and whatever you put your finish coat over must be 'glued' 100% to the base metal AND must allow your finish coat to 'glue' 100% to it.
There are hundreds of formulations of paints, primers and reducers (thinners) and some don't mix well with others. Having a paint job lift as it dries will ruin your whole day.
The recipe is to prep it right, prime it right and paint it right...the first time. Good luck and it sure wouldn't hurt to go to a automotive paint store near you and chat with one of the guru's, they love to share good info.
Carpoor is right, if you do the spray bomb, you will have to sand it all back off before coating with something else. The spray can material will do little to keep the moisture out, so store you stuff inside.
Stuart
