Mar-K has a few comments on the por15 and top coat in this forum under Bed Questions. But, even as they say, its best to follow the manufacturers instructions.
Tim, the cheap throw away brushes will "shed" a bristle here and there but presented no big problem. I have one here and there on my chassis but I left them for "character" and to also watch and see what happens!
This stuff will dry or skim over pretty fast. So, don't pour a lot out of the can at one time. Keep the can covered really good. One stovebolter suggested drilling a small hole in the top and then just sticking some duct tape over it to keep it from drying out.... pour a little as you need it.
Don't worry Tim, you'll learn fast!!
