It can be brushed on, or you can use a card (old gift card, credit card, etc) to apply it. It came with a little cardboard spatula. Once it's dry it's waterproof (obviously seams wouldn't be) and can be wiped clean, or it can be machine washed (but probably not machine dried). I think it's silicone based. It comes out of the jar very thick and gel-like. I did a test piece so I could see how my machine handles it and it was fine. I used a teflon foot and a titanium topstitch needle, although other needles would probably work fine. I used 3 coats and it's a little shiny, but not glossy. I'll probably only do 2 coats when I make the bag.
Click here for the website for it.