Back home from work with a little more time to write an proper answer Ill try to develop the technique some more.
I thin with Lack-Nafta which is a local stronger version of White Spirit. White Spirit or Essence the Petrol works just fine.
A good tip is to put on the base colour and let it dry for at least 24 hours. Just little or none thinnings is required, just enough to make the paint smooth. 2-3 layers is usually need with the execption of yellow which can be a real pain in the you now what.
When basecolour is dry, start painting first shadow. The paint for highlights and shadows should be more diluted, to a point that it almost doesnt cover. Let the paint be until the surface looks dry and then blend it by dipping the brush in White Spirit etc. Take a rag and drag the brush through it so only little , little sovent is left in the brush. No solvent should come out from the bristles when you touch something with it but the bristles should feel a little damp. Then start blending by dragging the tip of the brush along the edges of the shadow or highlight to be blended. With a little more solvent in the brush it can be used as an eraser to correct mistakes or trimming lines that could need some touch up. Wait over night to led dry before putting on the next shade of shadow or highlight.
Its a bit slow method but on the other hand your playing it safe to have every shadow and highlight thorougly dry before putting on the next. When you feel more secure you can use a hairdryer to speed up the process and do all the shading and highlights of a certain colour in 2-3 hours or less. I know Mike Blank works with Humbrols wet in wet but I think Im not ready for that yet. :lol:
