Thanks folks.
The process is pretty straightforward, a base of midtone (in this case screamer pink) 2 thin coats. Then start shading the recesses with successive layers of very thin shade tones (Screamer pink, some Scale 75 violet) brush in the highlight then quickly wash the brush and wash the edge with the clean brush to remove any watermark etc.
Continue this process and i added some flat black to the shade layer and brought the shading line down to just the very bottom of the recesses.
I then painted the random line pattern on the cape (as its supposed to be random as Tzeentch would like, i didnt use a pattern but had a think about it first!) then i re did the shading process again over the lines i painted to bring it back into the coat rather than seem like something on top.
Its very important to let each glaze dry fully before the next, i use a hairdryer to speed up the process.