Thanks for the replies!
@Jim I agree, I don't want to buy a 5 gal pail of the stuff.
@Brendan Thanks, I didn't know about shoe goo. Do you think white gas would be ok to dilute it?
@Valerie I want to seam seal a PU coated 2006 REI Quarterdome. From what I've been reading, an urethane sealer is recommended. I haven't found people claiming silicone sealer works on PU coated fabrics, but it may very well work, especially on the non-coated side of the fabric.