I'm old fashioned in that I really only use three colours to obtain the look I am going for. It will be a dark base colour (in this instance, it is Khorne Red), the brightest layer (Evil Sunz Scarlet), and Abaddon Black.
I put a decent amount of the base colour on a wet palette, and will paint the cloak in that colour. I add a drop or two of black to the paint on the palette until it gets to the shade I want, and then I paint that into the recesses of the cloak. I then do a mixture of the base colour and the layer colour to work my way up to the final layer of just the layer.
If you look at the second last picture, you can see there are five layers of colour all together. The darkest two layers are Khorne Red and the Khorne Red / Abaddon Black mixture. The next two layers are 1:1 and 1:2 of Khorne Red / Red Sunz Scarlet. The last layer is just the Scarlet.