well sharkie   waterlox marine sealer aint cheap eather.......well keep it simple i use flex coat rod finish on my plugs but you have to spin the plug for a least 4.0hrs and let dry overnight  but u must mix equal parts of the stuff i use syringes to measure it out.......i also use devcon 2 part 30min epoxy and i spin that aswell on a rod dryer to prevent sags...........say after sealing your plugs and let them dry real good.....  i use 220 grit to smooth out the body's of the plug which  produces a smooth surface to spray your plugs..........oh dont forget to use a tack cloth to remove sanding dust ..................cheers mate!!!