Fellow modelers,
I am attempting my first winter whitewash on an M7 Priest. I have been using an old model as a test subject, and cannot find a good way of "scrubbing" off the whitewash. I tried a semi-wet toothbrush but too much comes off. A toothpick, and not enough. I let the hairspray dry overnight, then added valleo flat white, in 2 layers, again to dry overnight. A hard bristle brush maybe?
Thanks in advance!
Ziggy

I don't wait overnight, when I see the layer is dry, I paint next layer. You must add only one layer of white color.When see the white color is dry I start "scrub". Maybe there is the problem, you are waiting to long. The longest time I waiting is only a hour.

I can only echo what Pawel has said. Most likely you have let the hairspray and paint dry to long.

Are you applying a gloss coat, under the white wash?

No gloss coat. Just hairspray then paint. Since i am testing on another old model first, i will try gloss coat, hairspray, acrylic paint, and only let dry for an hour. But still, do i remove with damp toothbrush, toothpick, stiff brush? How much water or other liquid would/should i use?

I have only used washable white once which is on my current WIP. I can tell you that it was a PAIN to use and brush off. The first one I tried using a brush to apply the camo but the white wouldn't come off (not as easy as those seen in videos). I had to strip everything and apply the washable white using an AB. The fading was a bit easier but still not as easy as I expected.

Go to the craft store and get a cheap set of stencil brushes. These are useful sized and stiff bristled; perfect for scrubbing off white wash. You can use less water and have more control with these.