Ancestor paintover

I'm trying to practice a technique I learned at Artfest last year and make it my own. Long way from that, but this attempt was a lot better than my first. Thank you, Lisa... things didn't go so well in class, but I guess I learned enough to keep trying.
This is a higher-contrast copy of the original photo. (My grandfather is the guy seated on the far right.) Painting skin color would be tricky in any case, but man... these guys are brothers, and they're all different shades. All of them except my grandfather were long dead by the time I was born. So I'm kinda guessing what their skin tones were like in real life.
This was my first attempt at Lisa Bebi's "paintover" technique, at Artfest. (I've only had two classes so far in acrylic painting.) Not much time to experiment with mixing colors. I also did more of a wash than solid paint at the time. When I first posted that picture, Blaiz gave me the paint colors that would work for African American skin, and I practiced this week.
First, it helped to copy the photo a little darker and more high-contrast than usual. The eyes came out sharper, and the shadows didn't get blotted out so easily by the paint.

I mixed Transparent Red Iron Oxide (Golden) with Burnt Umber (DecoArt Americana) as his basic color, then mixed in a little Warm White (Americana) for the highlights. The shadows are Ultramarine Blue (Golden) blended with the basic color mix, to produce a muddied shade. It looked a little stark, so I washed it with the basic mix and that seemed to smooth things out.
This brother looked like he had more red in his skin. So I did the same basic color mix, except in a 2:1 ratio. Also washed the painted face with the 2:1 ratio.

Oh yeah -- the hair on both men was a wash of Burnt Umber and Lamp (Black) Ebony (Americana).

Not worried about the little bleed-over spots; I'm going to mess with this a little more. Then I'm going to scan the final piece and put it into a genealogy photo album.

Hey, does anyone know a way to scan something that has a transparency in it? Or do you really just need to photograph it at the appropriate angle with the right lighting? Thoughts?