> Roger, can you please explain your tip? Are you saying that this is a silicone spray
> and that you should 1st apply some sort of fluorocarbon DWR before this kind of
> silicone DWR spray can work properly?
Silicone spray leaves a soft and easily rubbed off finish. The silicone polymrs simply does not stick. It might be OK for suede street shoes, but it is NOT for back-country gear (with one exception).
The exception is a silnylon fabric. You can hit this with a silicone spray for a small improvement. You could for instance spray your silnylon tarp or tent once a year with silicone. Pitch the tent, spray, and leave sitting in the sun for a few hours to bond. Yes, surprisingly, silicone polymer does bond best to silicone polymer!
Now, techie details.
Silicone coating and fluorocarbon coating are fundamentally incompatible. If you use silicone spray on a fluorocarbon-treated fabric it won't stick, but it will prevent you from ever successfully applying any fluorocarbon DWR in the future. So never, ever mix them!
If you try to refresh the DWR without washing all the dirt off first, all you will do is DWR the dirt. The fabric won't improve. In fact, there will be (is) all sorts of 'stuff' on the fabric, even if it looks 'clean', which will be killing the DWR treatment. This includes skin oils!
If you wash your DWR fabric in the washing machine with ordinary laundry powder or detergent, you will be killing it. Read the label: apple scent, fabric whitener, bulking agent, enzymes ... and they do not rinse out! They stay on the fabric and kill the DWR. Stuff like Atsko Sports Wash is a pure detergent with NO additives, and it will rinse clean.
In fact, it has been recommended that in some cases you may need to run the fabric through the full wash cycle with Sports Wash twice, just to strip off all the gunk from trees, skin and washing powders. A dummy run through the washing machine to get the washing machine tub clean is sometimes needed! It's a hassle, sure, but it works, and not getting the fabric clean first ensures rapid failure.
Oh yes - you must do the heat cycle when refreshing the DWR. The heat is what bonds the new fluorocarbon to the fabric and the old fluorocarbon. Read the label.