Steven - Thanks so much for your thoughts! Usually I do work all around a painting but this is the first time I'm using an underpainting. And I think I spent so much effort to achieve the likeness, that I started in on the background as sort of a light, non-stress relief. Then at some point, I started avoiding the face, (you're right!

) because I do think getting it to look 'real' will be the most difficult. I had meant to at least do all the skin tones (arms and face) together but somehow still wasn't ready to mess with the face when I did the arms yesterday! Well, I can hardly avoid it anymore! Hopefully it'll still all come together.
Lisa - I'm a little bit overwhelmed by your comments! Thank-you
I think the only 'secret' I've got is pure determination to get it looking the way I want it to, regardless of how much time it takes. So far I've invested 38 hours in this piece, I'm not sure how that compares to someone painting a similar piece in oils, but I gather oils would be quicker? I'm using Liquitex high-viscosity acrylics. When I want soft transitions, I'm painting the base colors in first then painting over it with paint that's been watered down (sometimes to what looks like my kids' water colors out of the little plastic box). Or I'll dry brush over an area, then use just a wet brush to spread that around (or a moist paper towel to pull it off if I don't like it). I'm not saving colors (but probably should!), but use a fairly limited palette and know what I was mixing to get certain colors so that I can get back to the same color (or close).