any canvas waterproffig products that work out there,have a full cover that is soaking wet /looking for something that may be applied with a big sprayer ,thaks for any info

I had good results with the Starbright Canvas Waterproof Spray. Maybe its offered in a large container.

I recently bought a 1 gal .container of Starbright- it waterproofed A LOT of canvas. works well-

I use 303. Pour it into garden sprayer and away I go. Works well.

I use 303 High Tech Fabric Guard in a large sprayer.
It works great and its endorsed by the fabric manufactures.

Where do you get 303?

I buy a gallon online. Amazon or ebay. About $90 shipped

303 is awsum,and a litte goes a long way....

What is the best way to clean a cover?

IMO head off to the laundry mat and put it in one of those HUGE washing machines.