Yeah it's really easy. Just put your primer and base later on, then add in some of that oil! It will pool in the crevasses, and then continue to paint as you have (keeping away from those dark bits) and you'll have some lovely depth, nice and easy peasy@Disciple of Nagash
You're absolutely right that I do almost no shading, highlighting or dry brushing, just layers. Thats is also why I never did a showcase before
I did buy some Nuln oil and Agrax Earthshade just recently mostly to put on skin to pick out the eyes and mouth. But, that's about it. I'd never thought to put it on prior to adding layers though.
I'm not sure what tale of painters is but I'll have a look.