I use an airbrush to apply a zenithal primer, which is priming all black, then applying grey primer from a downward angle mimicking sunlight, followed by a white primer from directly above. I use Vallejo primer, thinned to an almost water consistency, then “spritzed” onto the model. Once that is done I take three paints: A dark Olive green, a mid-tone Olive green, and a highlight Olive green( Reaper Paints are usually provided in “triads” like this, it makes this step easier) I then thin the paints to an almost glaze consistency and wash over the parts that match the “brightness” of the paint closest. If part of the miniature is still mostly black, I usually don’t paint over it and leave it alone as a shadow.
The best part of these Resin casts is that there is so much detail if you keep your paint and primer thin enough throughout the process you don’t really need to paint too much. It really is just letting the airbrush do the heavy lifting of deciding where the shadows and light go, and just shifting the color enough to look right. it makes the model look desaturated and almost like watching a “colorized” old black and white film. It’s not a great look for GW style miniatures but I think it’s spot on for Fallout.