25$ paintjob?

[Mike 85]

The "thing" about leaving in primer,even 2K type,is contamination.Even inside in the shop or garage,it will pick up "whatever" happens to land on it be it WD-40 to simple moisture which WILL come back out later. No amount of cleaning or sanding,which will only grind the contaminate IN more, will remove it.
Epoxy is your only "real" answer. A cheap touch up gun can work fine for doing most any spraying.Might take awhile for a hood or such but those "little" guns will surprise you what all you can do.At least you got something "good" on for the time being and all you need is a quick sand with 180 and when you get a full size gun,recoat it and get on with it.
You can pick up a gallon kit of Southern Polyurethanes epoxy for less than $200 which gives you 2 gallons sprayable which will cover a LOT.Or, Get a qt. kit for less than $60 and have a half gallon sprayable.Their epoxy will last for years sealed up.I know,I have some 3 years old I still use out of. Once you mix it,you have a 24 hr. pot life and if you need more,just mix fresh and add to the old and you got another 24 hr.
Just don't expect "primer" to protect much.