This is a video on how to waterproof your boots. It’s really easy. Here is a list of cheap supplies you will need to waterproof your old boots.
Supply links from Amazon
eBay
Another thing that you can do that I did not bring out on the video is that you can heat your boots up in the oven before applying the mixture. This makes the mixture absorb even further into the material. You can repeat and polish several times to get a good watertight seal.