I just use the plain protectorant. I tried the fabric guard and it left residue. I mix up a tub of diluted - water and 303, no particular ratio, and saturate. Let it dry well, and then take a shower with it, making sure I rinse well everywhere.

Eons past I talked to Dick Kelty about why they were. Camptrails had a urethane coated bag that was similar in size, but much cheaper (and buying a Kelty on high school grocery bagger wages was a big commitment). He said any coating weakens the fabric, and added useless weight, since there would be leakage anyway.

So his solution was uncoated fabric, and a separate rain cover. Also, keep things out of the sun, which is the most common form of damage. The 303 is to try and mitigate the sun, the shower is to mitigate the 303.