A torturous process. Started with a continuous tone neg-print onto lith for positive, print lith onto lith for negative. Opaque to drop out background areas. Sandwich on light box, and re-photograph onto c-41 and print as ra-4. This scanner runs a bit coole; the original is warmer.
I remember reading about this technique in the 70s or 80s, I think in Todd and Zakia's _101 Experiments in Photography_. Haven't seen it done the old fashioned way for some time, but it works nicely here.