When you buy a cowboy hat, you're not only making a purchase for something to protect your head, you're making a fashion statement of some kind. You may go so far as to buy a Stetson brand hat, famous for its longevity and stand-up-to-anything nature. With such a hat, you want to take good care of it. It's a good idea to waterproof it before letting it see outdoor use.
Determine the type of waterproofing substance you need for your cowboy hat. Talk with the local vendor about the various types of liquids and gels, and be sure to take your hat so that you can find the specific waterproofing substance for its material.
Find a hidden spot on the material and do a spot-check on it. Rub in the waterproofing material and let it sit for several hours. When you are satisfied that the application of the waterproofing liquid won't negatively alter the color of your cowboy hat, apply the coating as directed.
Ask your vendor about the effects of the waterproofing liquid on your particular material. Some sprays, with water or silicone bases, will change the texture of your material. Be certain that you are OK with any particular change in texture of your cowboy hat before applying a waterproofing coat to the whole thing.
Clean your hat completely before applying waterproofing oils or sprays. Ideally, you should waterproof your hat as soon as you can after buying it, so it should be absolutely clean before you do this. If you use an oil, apply it liberally to the whole hat, work it in well with cloth or brush, and wipe away any excess. Allow it to stand overnight.
Use a spray, if desired, by holding the spray can six or eight inches from your cowboy hat. Spray in such a way as to cover your entire hat, and allow to dry.