Amazingly enough I appear to have found the solution to my problems with painting Trollbloods - other than to stop painting them. Since Madrak was the first miniature I've painted in over 4 years I have been highlighting up from the darker base color. I tried this with my normal trollkin and trolls only to find their flesh was a total pain to do and turned out too dark and looked very plastic. Instead I've started to shade down from the color I want the highlights to be, using the base color and washes to achieve the effect I'm looking for while retaining the brightness I wanted. It's not perfect but it's a damn slight better than before - and really fast too.
There are several other things I've done, I've ditched all the brushes I bought from Games Workshop in favor of a cheap packet of brushes that were on sale for the same price as a single GW brush and my new brushes (of the TK-C brand) are incredibly superior in just about every way. I also picked up a few paint palettes and the trollblood set of P3 paints, of which I've used Underbelly Blue (mistaking it for Trollblood Highlight at the time, but it worked out nicely) and Trollblood Blue. Mixing these P3 colors with some Asurmen Blue wash from Games Workshop to thin them down and make the shading washes darker and hey presto! fast, easy troll flesh.
I've started to wonder about GW paints, since they're all I've really used before it was natural to go out and buy heaps and heaps of them along with all the GW modeling tools (we can't get the Privateer ones in Glasgow) - but since I discovered the art store and the P3 paints I think I would have been much better off investing my money there. Almost all the tools I've bought from GW I could have got from the art store for much cheaper, the exceptions appear to be the jeweller's saw and the files. So my advice to anyone thinking of stocking up on all the modeling and painting equipment: BUY IT FROM THE ART STORE FIRST. Use the gaming store to get what you can't get in the art store. Oh and GW paint brushes suck goats.
Another thing, painting warjacks is so stupidly easy, I could paint these things all day. My Magnus battle group is already 50% done, will need to start on Magnus himself shortly but he can't be that much harder. All I need is more renegades...