Waterproofing canvas

[Beeman]

You might want to try this. Find someone in your area that sells or services RVs like tent trailors. They usually carry large cans of the waterproofing that is used on the canvas of the trailors. Get some and then go to Home depot and buy a cheap pesticide sprayer. ($9 or $10 bucks for the plastic 2 gal ones) Set up your tent on a nice sunny day and use the sprayer to apply the stuff in the can. It works pretty well and its easy to do.

[Ismaels-Legacy]

You could always turn that canvass into Oilskin by applying a coating of Beeswax dissolved in Linseed Oil.... I'm not sure about the exact amounts, but there's a recipe for this floating around the 'net somewhere.