Folks, i dont recommend using Repel as a wash in solution. 2 reasons, firstly its very difficult to get all the detergent out of a washing machine, so though it really helps to be fully washed and dry before application, any detergent will work against any water repellent, so may kind of nutrilise the effect. The other issue is the dilution factor. Repel uses similar chemistry as many other repellents, but I just make it super concentrated. The chemicals are not furiously expensive, but bottles and the like are post pandemic, so its not a problem for me to make it very concentrated, and thats why we get very good results. Its actually water based, so it will work in a machine wash, but basically you take a concentrated solution and make it very dilute.
The best way to apply it is to a clean and dry garment. Warm the bottle in a cup of water and then spray it on, then rub in, get it good and wet but not dripping, its a waste. You cannot do a 2nd coat, once repel is dry it repels itself, as its water based, so give it one good coat. The matrix the active ingredient is suspended in will set in low temperatures, most others will not and this was specified, as we designed if for breathable waders and breathable waders and jackets cannot survive heat - not even the heat of a car on a sunny day! However the more heat you dry it with the more the reaction you will see. Now the clever bit. Imagine repel is a net, and the active ingredient is tennish balls. Over time the tennis balls wear, and the reaction is reduced. But if you then heat it again, even just using it on a sunny day, then the net will "melt" and the tennis balls move, so the reaction starts all over again. My argo canopy and boat bimini were treated 4-5 years ago, every sunny day they reactivate and so years on the reaction is still excellent.
Hope this helps, i am happy to help and advise on Repel. Thanks to Paul for letting me know about the thread, i missed it yesterday!