Did mine a few months ago as the link in Scott's post suggests. I used a new Hudson sprayer to spray the 303 on it. Used about 1/2 gallon. If you used a paint sprayer you could probably do a better job. I will probably do it with my spray gun the next time around so I can get it more even. The little spray bottle is good for touch-ups.
My sunbrella cover got cleaned in an industrial washing machine (Laundry mat), then I added in Nikwax to the second cycle. Same stuff I use for all my outdoor clothing that I want breathable yet waterproof, like Gortex.