I've had pretty good luck w/ 303 high tech fabric guard.  It's solvent based, so you'll want to roll the gaskets inside the top before spraying and wipe off any overspray w/ soapy water as soon as practical.  The last time I did mine, I sprayed it at night in my garage, put a second coat on about 3 hours later and the next morning it was dry.  The DWR coating has held up better than the original one.  So, the only drying requirement is to leave it hanging - no external heat sources required - which is good since it's flammable until dry!

www.303products.com/tech/index.cfm