303 and RaggTopp are both excellent products and the key to both, or any similar product, is thin coats. That holds true with waxes and sealants, vinyl and rubber dressing, leather conditioners, etc. Heck, it's even true with spray paint!

An alternative to both products, and often locally available (which the other two usually are not) is Meguiar's M71 Canvas Cleaner and M72 Canvas Protectant. You can usually find these at boating supply stores like West Marine so you don't always have to order them online. Of course, if you live in Montana or Kansas you probably don't have a boat store near you