Penny Meyer posted an extensive tutorial on painting the relief bust of "Lincoln" on her blog at
www.flattinfigures.com. You can see it here:
http://www.flattinfigures.com/category/pennys-blogPenny takes you through her method of painting a figure in "grisaille" or grayscale, first. It is a rather extensive process, but she walks you through it step by step.
I saw the figure completed at a SCAHMS meeting today. Photos do not do her work or the Gary's relief justice. The figure looked like glowed. I took some photos of it and video taped her tutorial at SCAHMS and hope to have it posted on line in a few days. I'll let you know when and where it can be viewed.