My pleasure - always interested to share ideas.
Lance - you ask a very good question, and it's hard to answer! There are so many variables using this method. I can never remember if I go at it very soon after the painting of the colour layer after the hairspray, or is it a few days later??? I typically would attempt to create the effect within a day of spraying the colour coat. And it's a fairly thin one. And I use Tamiya brand thinner with my colour coat- is that a consideration, who knows!?
It's best to experiment on an older model first. I used an old Italeri Horch 1/35 staff car originally painted dark grey, and did a winter white wash on it. Used varying amounts of hairspray, overcoat, then decided how much water to put on the brush. The longer the water has a chance to soak the surface, the more paint will lift off. I have to say that too much of a wet scrubbing brush will peel off too much paint, so you have to be gentle, careful, and patient. In the end I still experiment with this - and ended up stumbling my way through this one too, to be honest
Cheers,
Gary