You might want to be careful where you use that stuff. Hydrophobic products do have some drawbacks so mask carefully where there might be something it shouldn't be on. And it's use on fabrics and the toilet brush are nice and showy, but impractical. I can't imagine it wares well enough for scrubbing with Comet or repeated washings in a machine. Never get that stuff on anything that requires regulr painting for maintenance. In fact I would look into whether or not it can even be recoated with anything, including itself. Otherwise you have a whole new set of problems with whatever you put it on. Let's say you use it on a vinyl boat canopy (or something) and the stuff can never be recoated.?. Once it starts to wear you'll get uneven, blotchy results trying to use normal vinyl protectants or even more coats of Neverwet. Basically, whatever you decide to spray it on, think it all the way through to where it becomes a problem to consider if there may be one.
My first thought was whether or not it might make a good finish for the back of a guitar neck for a sort of non-stick, PTFE feel. Or maybe use it on the rims of drum shells to mitigate all that popping the heads do as you tune them.