Revell No. 9 "anthracite grey" is a very dark grey that simulates flat black as seen through the canopy. Most Revell instructions used it for early jet interior.
FSM tips article tended to recommend using Dark Gull Grey (MM 1740) for the same. However, Dark Gull Grey is in fact a shade lighter than the "anthracite grey".
The simulation is scale dependent. Use lighter shade for smaller scale. Dark Gull Grey is good for 1:72. I will add a drop or two of flat black when used with larger scale. There is no set rule for how dark the scaling effect needs to be. Try different shade to get what you feel to be most natural for your taste.