um they sale, a tar like sealer at home dummy or lowes, you kinda pour it on there and spread it around with a broom looking thing . this is the stuff you should look for, or something relativly close to it
http://paint-and-supplies.hardwarest...ng-629219.aspx
ive used this sort of stuff before it works really well, just make sure you do the whole roof at the same time or you'll be able to see color differences oh and mix that bucket like theres no tomorrow
good luck