Hi Pedro,
Yes, I mask the ribbing of all parts are fabric coated on the real plane. Basically my technique consist in Airbrushing a base color ( normally slightly different from the one applyed on metal part on the real plane). Then i Mask the ribbs with jammydog tape (you can find from 0,5 mm wide, 0,75 mm, 1mm, 1,25 ecc...) then I airbrush the base color darkened, on the tape, trying to create the thin darker area you can see ust along the ribs. If the effect is too prominent, I spray very thinned color at low pressure, on the all surface, untill the contrast is toned down to the desired level. Tamiya and Gunze are perfect colors for this job, since can sustain a very high thinning rate ( up to 8 part of thinner, 1 part of color), keep in mind once the plane is fixed on the base, the lower surface are not reciving too much light, therefore dont be afraid to exagerate the effect on the undersurface. Some picture of my 1/72 Corsair may clarify:
Pic 1. The contour of the fabric area is masked.
Pic.2 The lighter color applied is well visible.
Pic.3 Ribs are masked.
Pic.4 Darkened blue airbrushed on the masking tape, and finally the tape is removed.
