Welcome to the site.It kind of depends on the system you'll use to paint it.If there's no bodywork and you're just holding ittill paint I'd DP it in PPGs system (without reducer),but you'll need to let it sit for a at least a month before it'll sand nicely without balling up in the paper.Actually the best thing to do I think is singlestage it in the closest solid color to what you want and drive it.When you're ready to paint wet sand it down without breaking through and base right over it using it as the sealer,the best sealer I think as long as it's cure out.2 coats of good paint will cost a little more than the sealer as long as you're not into expensive colors like red,but I think the end result is worth it.