Thanks Rick, Nigel, Andreas and Allan.
I followed Haris Ali's suggestion of pre-shading the fuselage structure of the Pup. By airbrushing over the shading and rigging lines, the effects are quite subtle in these photos, but adequate for what I was trying to achieve. It's possible that this was all a complete waste of time & effort once I've added the eventual weathering...but one is not certain until the end of the process


Internal structure was sprayed with XF-15 Flesh, then masked.

The tapes were lightly sprayed over with NATO Black XF-69

Removing the tape revealed the pre-shade pattern

Airbrushing XF-55 Deck Tan (for CDL) muted the pre-shade

pencil lines were drawn onto the fuselage to mimic the internal rigging (not quite that well as it looks)

The internal rigging pencil lines were muted with more over-spray of XF-55