I just started on Nancy, a 75mm figure from Neko Galaxy. I've been focusing on improving my use of light and my skin work lately, so I thought I'd share some details of my approach for this figure.
I've been painting cast shadows on my last few projects and I find taking reference photos to be a huge help in making sure my cast shadow placement looks believable. A simple way to do that is to take the unpainted figure and place it under my painting lamp. I can then move the light around until I find an angle that I think works well with the figure. Be sure to keep in mind what your intended 'front' view for the piece will be when you picking your light placement!
For this piece I ended up taking two different series of reference photos, one with the unprimed figure and one after I'd primed her. Why? Well, on the unprimed figure you get more of a semi-gloss reflection off the bare resin. I wanted to create a similar shine when I painted the skin, so the unprimed pictures help me place those reflection points and understand their shapes. Now these reflections will change depending on what angle you're viewing the figure from, but if you stick with whatever view you think is the front, you should be fine. The second set is after priming. The figure now has a matte finish so it's a little easier to isolate the shaded vs lit regions. You can still get that information from the first image, but I think it reads clearer in the second.
Jump forward to the painted figure and you can see the placement of shadows on the skin based on the reference photos as well as the reflection points. Of course you don't need to match them exactly, you can use your artistic license to make adjustments. For example, I've maybe pushed the shadows a little further towards the side on her face to keep it well lit. And I've added some small reflections to bring out the knees more. But overall I've stuck close to the reference photos and used those to help guide me as I painted.
As for colors, I recommend not getting too caught up in specific paints. You don't need this particular shade of red from this particular brand of paint to get similar results. Rather focus on the colors themselves (that blue was used here and yellow there, whether the colors are light or dark, saturated or desaturated, etc) and pick similar shades from whatever brand you prefer. Okay, end of disclaimer! ;D
I've got a mix of Reaper and AK Interactive paints. For a base, I used a 50/50 mix of Reaper's Rosy Shadow and Fair Skin. The darkest shadows were Reaper's Ruddy Leather mixed with Imperial Purple, Void Blue, and Rosy Shadow (something like 2 parts Ruddy Leather, 1 part Imperial Purple, 1 part Rosy Shadow, and a touch of Void Blue). Normally I'd substitute the blue for purple, but I wanted a more violet ambient light for this scene and hence the change. If I needed anything darker, I'd use the same mix but remove the Rosy Shadow and add in more Purple and Blue. From that shadow mix, I'd work in layers up to pure Rosy Shadow and then continue on until I reached the 50/50 Rosy Shadow and Fair Skin mix. For the highlights, I then began to add a 2:1 mix of Reaper's Lemon Yellow and Linen White into the 50/50 Fair Skin and Rosy Shadow mix. I wanted a yellow feel for my primary light source but if I worked up to pure Fair Skin first, that color would be about as light as the yellow is and thus it'd no longer work for the highlight. So I begin when I've still at 50/50 Rosy Shadow and Fair Skin.
For the reflection points on the skin, I started to add Pure White to the highlight mix but prior to reaching pure Lemon Yellow/Linen White. I liked the results better when I switched over to adding white while there was still some skin tone in the mix.
Using the same approach as above, I also added red to the shadow tones and midtone (darker red into shadows, lighter red into midtone) and used that variation in areas like the nose, cheeks, and knees. However, I kept the same highlight mix rather than adding red there too. I then use intermediate mixes between the red variant and the main skin version to blend the transition regions. You'll see I still need to do some adjustments around the knees.
For the body suit, I switched over to mostly AK Interactive paints just because those are the shades I had handy. The base was AK's rock grey, a warm grey. For the shadows, I took a bit of Amethyst Blue and Strong Dark Blue (50/50) for a nice dark violet which will be used throughout the rest of the figure. I added some of that to AK's Neutral Grey. I began with that grey-violet mix for the darkest shadows and then gradually worked up to almost pure grey. I wanted the body suit to look white, not purple, so I tried to find a balance between adding in some of the ambient color without so much that it overpowers the primary color for the suit. Into the mix of mostly grey with a little violet, I then added Rock Grey. When I reached pure Rock Grey, I then started to add my Lemon Yellow and Linen White mix. Since the base color here was already pretty light, I switched up the highlight to a 1:2 mix of Lemon Yellow and Linen White (more white than yellow).
I'm debating if I also want to add pure white reflection points on the body suit to give it more of a shiny look. I'm going to hold off for now and wait to see how things look with the metal portions done. Speaking of which, the armor is based coated with that dark violet mix on areas that will eventually be metallic. Then there will be regions of painted metal, which I've based with a 50/50 mix of AK's Burnt Red and Medium Rust. I'm sticking close to the original concept art, but swapping the yellow in those for red just to make mine a bit different.