So here's my nearly-painless method for painting yellow:
1) After priming (I used grey here, white would probably work, but could be brighter? not sure about black... it would probably just take more pink), base coat the areas to be yellow in a nice bright pink. I used a 40/60 mix of warlock purple and skull white, but any bright pink should work. But make sure the pink coat is smooth and solid before proceeding (about 2 or 3 layers)
2) Cover the pink with thinned layers of Golden Yellow. Again, this took me about 2 or 3 layers of very thin paint to get to. You should notice the pink showing throw now looks a golden orange.
3) Give the whole thing a wash the yellow in gryphonne sepia.
4) Soft edge highlight with golden yellow:
5) Get the deepest recesses with ogryn flesh wash, add some thin edge/corner highlights with sunburst yellow:
And voila! It's a very luminous / rich yellow and although there's many layers too it - it's not super complicated to pull off. However there are two things to be aware of.
1) Because there's so many layers here you really need to make sure your paint is thinned. The normal description is of skim milk, I went a little beyond this and it worked out well.
2) Since the color we're making is fairly complex, touch ups are a real pain. Though I did the yellow first here, it would probably make things easier to do the yellow last when painting the mini.
And here's the finished product:
Hope this proves useful to someone!