Hi,
I am by no means an expert, but I have been painting mostly 6mm in the last year so here are my thoughts.
- Have you looked at the painting tutorials on the Baccus site? They really are the best around. They are though, based on black primer. The black primer helps as deep shadow and makes the dabs of color pop.
- Given that using black primer is out, I would drybrush a highlight and then give the whole figure a wash. I have played around with this approach and like using the Coat d'Arms shaders over the Army Painter shaders which I find to either too dark, or too pale depending on the shader. I mix the Coat d'Arms black shader and the dark brown shader, I find the slightly warmer tone helps in the small scale. Then again I am mostly focused on ancients.
Best of luck! I found 6mm frustrating at first, but once I was able to shift my approach (per the Baccus tutorials) I have found them great fun and much less stressful than the larger size figures.
Martin