The only thing I can tell you is if you are going to use one of the previously mentioned Filson/Barbour waxes, use your fingers, go slowly and work it into the material. The key is using heat to impregnate the fibers rather than "painting it on". once you start doing it, you'll understand the process. If you still have concerns, do a small practice session with a spare piece of cloth. This is how I would apply the wax in an attempt to just waterproof the cloth.
For heavy brush busting power, then the paint brushing method is better, but uses a lot more wax.
