I was not always a good painter. I estimate that I ruined about 2,000 points of white Tau and 2,000 points of muddy Blood Angels before I got my painting feet under me. In this time that I was ruining minis with paint and and not painting them, I talked to an artist that painted minis masterful. She was painting a giant Skaven mini and showed me a picture of what she was going for. I was confused because she started by painting it a medium tan (like Graveyard Earth) and she wanted to end with lite skin tones (like Elf Flesh). She told me that painting for a dissimilar (and sometimes contrasting) base color adds depth to a mini in ways that layering can not.
I told her that I thought that she could metaphorically fertilize a field with that.
Then I tried it.
I started by trying something simple like painting daemon skin. Little did I know that painting daemon skin is one of the challenging and complicated things to do. I took a shot in the dark and painted the severed head of a Bloodletter on my knock off Sanguinius mini purple as a base coat for red. It turned out pretty good and the blue in the purple paint really made the red pop. Overall the head looked brighter with fewer highlights with this technique.
Experimenting with this head directly lead to me developing the step-by-step Bloodletter post and the 10 Bloodletters that sit in my collection.
This lead me to think about how I could paint flesh in other interesting ways. Just for fun, I painted the Plaguebearer head on my Grey Knight Justicar's base Bleached Bone and washed it green. I loved out it turned out. With a little but a modification I had a technique that served me well in painting my Daemon Prince of Nurgle and Nurglings on Typhus' base.
I expended and refined the technique to paint the Plaguebearers recently. I was less heavy-handed with the washes and ended up with a delicate and complex color scheme.
My intention is to paint the Reaper Great Worms as Beasts of Nurgle in the same fashion as the Plague bearers. They are going to end up green and red around the mouth but I started by painting them Bleached Bone and Hormagaunt Purple first.
The short of this is, eperiment with colors, layers and base colors even it seem silly to you at the moment. Use little decorative pieces to try new skills before you try them on full units. Use painting those full units with already tested techniques to further refine your new skills.