Are you thinning your washes correctly?
They should appear to look like 'dirty thinners'
I had the same problem when I tried acrylic washes, this is because acrylic thinners would eat through the Future (Pledge here), and leave a dirty ring.
I no longer use acrylics, only oils.
As long as you have thinned the wash right, you should have no problem with the Future being rubbed away.
I mix 10% paint to 90% thinners, this gives me a very light wash, but I would rather do it twice or more, than damage the paint work underneath.
Sounds like your trying to rub off a heavy paint layer, not a wash.
Also allow your Future layer to cure for at least 48 hours. And when removing the wash you applied, wipe it gently, going across the panel line in the direction of air flow ie front to back.
If the surface starts to feel a little bit 'tacky', that indicates you have started to wipe into the Future layer, just stop for say hlaf an hour, and try again.
Check out this sight-
http://www.swannysmodels.com/Weathering.html
Swanny is pretty much the guru round these parts.
Hope this helps a little