hey! I'm not sure what a oleo technique is but i hope some of my critiques might help, first your background looks uneven and thin using more paint will help cover it up and hind the messy brush strokes. from what i see you seem to be using a strong lighting with a bit or orange back light (sorry if I'm wrong) but i think your darks are a bit too dark since you seem to be using pure black, maybe mix it with a bit of a blue (since warm lighting=cold shadows) to tone it down or add more orange lighting transition from the back light (something like in the pic below) another thing i see is the highlights on the face seems a little grey. here's a quick paint over i did to make my explanation more understandable, overall you painting looks awesome and keep experimenting with strong lighting! hope it helps