I applaud you for thinking outside the box. If you have a gallon, then you probably know the manufacturer and can find out what kind of primer it needs. Of course, surface prep is the key to any coating or lining job. For coal tar epoxy we usually specify a pretty rough white metal blast. Check with the paint manuf.
How would you apply it? A brush or roller may be better because then you don't breathe as much of it. Also skin protection is a must.

R.