I found when I upped the concentration it left more streaks if it started to dry out and as you saw, even wetting it didn't help much, but with close to the recommended it was fine.
It's not great but for £3 what do you expect ? I just do contact less washes now, Koch Chemie Green Star 1:10 dilution prewash on body and wheels, then that AA Snow Foam from Home Bargains and Blow Dry the car ... no need for shampoo - works well and zero swirl marks ...
