I've used this waterproofer on some suede boots...a cloth hat...and some leather gloves.  Method used is to clean and wet the object to be treated using plain water...then spray the material on the surface where it soaks in...then let it dry.  After drying...it really makes water bead off of things.  Seems to work on any material that will wet with water...leather...cloth...etc.

The spray nozzle could be better...best to do this on a newspaper.  Not sure how long the treatment lasts...but the boots still bead water off without the leather wetting any.

**  after wearing the cloth hat in the rain for around an hour or so...I found that the waterproofing completely failed and that the hat material was soaked....not sure whether this material is synthetic (probably) or cotton.  The suede boots did much better and only a few spots seemed to get wet.

So my guess is that this waterproofer works well on natural materials like leather or cotton...but not on synthetics like nylon or polyester.