I'm attempting to thoroughly understand the DWR coatings and put more light on this crucial, and yet misunderstood piece of waterproofing. But from what I have found online DWR is little talked about beyond brand recommendations. I hope this thread can help elaborate on the details behind DWR, naming the ranking system, miles of wear before need to re-apply, and hydrophobic qualities of each type.
So far I understand there are three different kinds - wax, silicone, and fluorocarbon. Fluorocarbon reapplication time is longer than that of silicone, and longer with silicone than of wax. Fluorocarbons have the added benefit of repelling oil and dirt but are less enviornmentally friendly. You can't apply a different kind of DWR over a previous applicant... so you can't use Repel-X (fluoro) over NikWax (wax).
There are also two application types: wash-in, and spray on. Wax and silicone-based DWRs don't need post-application heat treating but fluorocarbons do, in order to activate the hydrophobic heads. Silicons and waxes are good for boots and leathers, things that can't be heat-treated. Soft shells and hard shells benefit from wax and flourocarbons, the difference is whether you have access to heat treatment at the time... so a wax-based DWR may be best for thru-hikers.
That's about it. I don't know if Deluge is better than Grangers, or if Scotchguard is more than just a brand name or if it really compares to the 'official recommended DWR brands' from names like Arc'Teryx and Patagonia. Can anyone help add to this discussion?