The main reason for washing is to give the re-proofer something clean to key to and to maintain breathability of the outer for the Gortex liner.
Don't worry, your kit won't come up looking shinny new, you'll still be a dirty biker..........
Or, get yourself a DPM Gortex over jacket from Anchors for £30. That's what I use, it folds up small enough to go in the Tuaregs bum pocket and your jacket will not even get damp.
Andres