I have been playing with this popular technique (of which I have posted some tips and tricks some day ago here) over the past days quite a bit and learning something new, so here are some more (hopefully) helpful ideas:
When painting my models, I am normally proceeding quite fast and apply as many paint layers as I can (mostly limited by time) in one session. Using Tamiya paints is very convenient for this as these paints dry very fast and are touch dry in really few minutes. This allows me to apply preshading layer and right away base and sometimes even highlights (or modulation as it is popularly called these days).
Now I have found that this does not work with the application of the hairspray technique. I was puzzled why in some cases I was not able to lift the second color while I have had no problem with this before. I realized that this problem occurred when I have applied the hairspray and the top color right after the underlying base color. I assume that the base color not being completely dry absorbed the hairspray and it was thus not possible to remove it with the application of water. The same was the case when the hairspray was applied on a “fresh” layer of gloss coat.
When I left the base coat dry overnight, I was able to lift the hairspray and top color easily even without the application of gloss coat beforehand (I only added 10% of Tamiya Clear into the base coat).
When using hairspray technique I was always afraid that if I let the top paint layer to dry too long, I will not be able to remove it. But after I eliminated the problem as described above, when I applied water on the top paint layer shortly after this was applied, the paint was actually dissolved too quickly. As described in my previous post, the result was that the paint was removed in large chunks and the transition or “weather” effect was lost. To avoid this I have not applied water on the top paint layer, but only slowly removed the paint with a brush that was moist only, I removed most of the water on the brush using a paper napkin. In this way the paint was not dissolved immediately, but in rather slow fashion (sometimes it felt as it is taking too long), but in the end I achieved the effect. Alternative solution I assume would be to let the paint dry a bit and start removing it afterwards. Will have to test it and will let you know…