I brought mine from Wal-Mart & put it on the top with a roller. A 5 gal. bucket was only about $40.00 it is a plastic fiber coat for roofs(I think they used it on the old tin roofs)but it works.I can't remember the name either but you get it in the paint section.Get you a roller open the 5 gal. bucket dip the roller in the bucket & roll it on"Simple"
It took about 30 mins. to do the top of my 40' GN trailer.