3M Scotchguard. Or Sunbrella . Some Ace Hardware stores carry the Sunbrella speay product for waterproofing & UV lprotection. Scotchguard doesn't have the UV protection but is excellent for waterproofing. I use it on the cheaper canvas covers. Spread cover out upside down, soak it down, let dry, do second time, let dry again. Flip it over & do top side 2 coats letting each coat dry before applying second coat. Seals,waterproofs, & keeps fibers soft. Takes anout 3 cans for a 20' cover.
92' ChampioN 201DCR Elite