Thanks!
Alistair, I have done the translucent effects in the following steps:
1) draw the wing spars and ribs with black permanent pen (Faber Castell) - as mentioned earlier, unlike others reporting problems, I have never had issues with pen ink bleeding under acrylic paints
2) airbrush the clear doped linen colour (Pactra acrylic A123)
3) mask and airbrush the checkboard shadow using a "clear" mix of Vallejo Beige Brown and clear gloss lacquer (around 1:10 proportion)
4) mask and airbrush the shadow of "5" using a "clear" mix of black and clear gloss (around 1:10 proportion, too)
Masks were prepared based on the decal dimensions - drawn on a paper and cut from pieces of Tamiya tape.
The tips of the wings, where original Italian green and red was painted and then scraped or overpainted in Polish service were not translucent.