Hi Stephan
The first problem was how do I blend them, as an oil painter I wanted
to have smooth transitions of colour.
I solved this one after reading an article by Mario Fuentes that appeared in
Historical Miniatures a very good U.S. publication. He works with dilutions
of colour to give transitions, which are not blended in the true sense, as oil
colours.
They are in fact separate washes which combine over a base coat creating
shading and highlights to achieve an effect known as visual blending.
For further reading I would recommend "Over head Lighting" books 1&2
also any article by U.S. painter Doug Cohen.
Hope this is of some help
Frank