The RGB mixer is a fun tool -- don't just settle for sat = 0%. Uncheck preserve luminance levels and then re-mix the RGB contributions. Real Black&White stock does not react to the color world the same way that RGB or CyMk emulsions do. It was designed to make flesh tones pop and its why the golden age actresses glow. Edith Head was famous for those pink sunglasses, but they were there so she could get a vague idea of what her wardrobe would like like monochromatically.
Do not overlook re-directed lighting. The classic Dashiel Hammet stories feature high-key and backlit edges, with mysterious cookies (notably half-lit shadows through venetian blinds, which are also designed to emphasize those dangerous curves. "Charlie bars" can be achieved with judicious power windows that direct the audience to various actors' features, whether it is her "charlies", I'm just relating the history and the nomenclature... or somebody's plotting eyes.
Film Noir at its best is a thin, tight surface over raw naked emotions. Go rent "Out of the Past" and then watch "Against All Odds."
"I always pass on free advice -- its never of any use to me" Oscar Wilde.
Very true -- a lot of the whole film noir thing is the lighting. There's a great quote attributed to cinematographer James Wong Howe who said, "it's taken me 40 years to learn, not how many lights to use, but how few." It's more about placing shadows than where the illumination goes.
If you've got something lit flat like a sitcom, it's never gonna be in a film noir world, because the deep shadow content just isn't there.
BTW, just to add to this: there was a fantastic film noir show on last year that nobody saw, the American TNT series Mob City. Several episodes were lit by the great David Tattersall, and I thought it was a remarkable looking show. The story and acting were flops with the critics, but I think it's one of the nicest-looking period shows I've ever seen, especially in the last few years. The fact that this was all shot with Arri Alexas and graded digitally, yet looks very close to a classic 1940s cop mystery, is really remarkable. It shows that you can preserve this look and still shoot in color.