This article contains a simple recipe for making a Beeswax and Oil based waterproofing.
There are variations on the recipe, given in the article
http://www.offthegridnews.com/extreme-survival/the-2-ingredient-off-grid-waterproofer-anyone-can-make/This works well (I have made my own in the past) for leather (shoes, straps) and for woven tent fabrics. Particularly good for the older fabric tents. Not so useful on the nylon fabrics, but it does increase their ability to shed water.
If you try this on plastic materials, DO TEST to be sure the plastic does not soften or melt with the application of the solvent in the mix.