I have both Arcteryx and Pattagucci - all either 2 or 3L Gortex... I found this video on Arcteryx website and have used this method on both brands (Pattys website pretty much outlines the same process as Arcteryx) and this method has worked flawlessly for me...
https://www.youtube.com/watch?v=I4N6ZuKTZ_c