[RolandF]

Those paints were washable insofar they could be removed by simple solvents like plane fuel. Too little solvent caused smudged areas.
Those paints were resistant enough to cause bright areas where the original camo was not exposed to weathering. Happened when it took a certain amount of time between application and sponging-off of the StKz. The StKz could be removed completely - just look at placeholders of letters where a fuselage band was applied by masking off the letters.

Regards
RolandF