I'm also talking about mixing colors to achieve the right shades. When I last used Tamiya paints on figures, some 10 or so years ago, I had been mixing their flesh with red brown to achieve a realistic flesh tone with the original formula. I got some of the new formula and the paint was drying on my palette and wouldn't respond to adding water except to loose any adhession.
You'll also find that if you lay down a brush stroke, it will skin over almost instantly. When you run your next brush load of paint, any contact will dissolve the skin and lift the underlying paint.
There was a time, from its introduction to the early 90's, when Tamiya paint was about as good as it got, brush OR airbrush. I knew guys who painted good looking cars by brush withthe old formula. I won a good number of awards with figures, autos, aircraft and armor with Tamiya painted models.
Unless you're willing to paint your figures one stroke at a time, with perhaps an hour or more of drying time between strokes, you should look into other brands. If you can't find them locally, there are numerous dealers on-line who carry Andrea/Vallejo.