I only use clear water to wash the soft tops. To dry I use an Absorber chamois and do not rub it on the top. I just place it flat, let the water absorb and then move on to the next area of the top.
I also do not wash the tops every time I wash the Vipers. Usually I wash the car just to get the dust and light road dirt off and If the top is down or off, it doesn't really need it.