Here's the trick to saving the POR-15 after you open the can. Empty it into a pint sized Mason/Kerr jar. I got a case of them for a couple of bucks, get the wide mouth ones. For brush painting, squeeze the brush against the inside of the jar only half way up. Do not get the paint on the lip of the jar, if you do, clean it immediately. For spray guns, pour it in the glass jar, use their solvent and pour a little in the can, seal it, shake it up real good, and pour it in the jar, do it for brush painting also, then thin as necessary. I use a coffee stirrer to mix the paint/solvent. When done with the spray gun, run some solvent through it, then I disassemble it and put the whole thing in a container of Zylene. It's fairly cheap by the gallon at Home Depot. Also it will clean up any misplaced POR-15. I only use their solvent to thin the paint for spraying. I've had the paint in the spray gun for over an hour waiting between coats, and have had no problems with it drying in the can. For spray gun use, you have to have a respirator and use latex gloves, cover bare skin with vaseline or you'll be wearing the paint for days. HTH.
Ron