the only places the canvas should be possibly leaking, is at the attachment points. the seams shouldn't leak once they've swollen and if by chance, they are, then regular tent seam sealer would be the choice.
of if the OP is actually having condensation issues and not true leak issues.
can't see how the stuff to dip tools in, could be used in this case.
but with a 13 year-old hybrid, there could be a variety of possibilities.
__________________
Dan-Retired California Firefighter/EMT
Shawn-Musician/Entrepreneur/Wine Expert
and Zoe the Wonder Dog(R.I.P.)
2016 PrimeTime TracerAIR 255, pushing a 2014 Ford F150 SCREW XTR 4x4 3.5 Ecoboost w/Max Tow Package
4pt Equal-i-zer WDH and 1828lbs of payload capacity