Hi Manni,
The washing liquid, just one or two drops in an amount of the wash will be enough.
Best to decant the wash into another container to use as it will get easily contaminated with brush residue from other products.
It shouldn't matter how much you apply or if it dries in dark spots.
It's water based so should remove with slightly damp paper towel or brush.
If necessary you should be able to remove it all and start again if you don't like your first results.
Really wet the dried on wash to reactivate it and wipe or brush it away.
You can even airbrush straight water over the surface to 'blast' it away.
Remember the more matte the clear coat applied, the more the wash will grip and the less you'll be able to remove.
I usually clear coat the painted surfaces with a semi-matte,
Mike
