This isn't a stand-alone product, but if you're doing any work with Gear-Aid adhesives (freesole, aquaseal, seam grip), you definitely want to do the job right and prep with this stuff.  It's a surface prep agent, thinner, and accelerator.  I recently used it to seal some very heavy-weight fabric: I painted the seams first with Cotol, then thinned Seam Grip with some more Cotol and applied it.  I could see the seam grip wetting out the seam quickly, as i applied it.  The seal went right down into a tight, stiff seam.  I was very happy!  Keep in mind your repair will set up faster with this stuff in it, though.

If you're doing something like shoe repair with Freesole, i'd suggest just using Cotol to prep the surface but not thinning the Freesole with it, to make it less likely to run and drip.