Steve,
Thanks. I'm hoping to get this right sooner or later. I find that I'm more comfortable trying to work with camouflage colors than I am with base colors in a more decorative setting. But I'll need to learn for that future red triplane.
But, my new Airbrush arrived today. It has a .2mm tip and can spray a very fine line of very thin paint without making paint spiders. Do you guys have a name for those paint smears that shoot out in 360 degrees?
So, I got to test it on my Alby's tail after having a few minutes on my paint hack. So far it has given me hope that I've made a good investment.

The base green I made by mixing Tamiya Enamel matte yellow and matte blue paints. The color just fell to where I wanted it.

The edging is untinted Tamiya matte red enamel. I sprayed it straight over the matte green I'd made.
Unfortunately there is a raised edge at the border. I'll live with it since I can't see it with my glasses off...lol

The darker green between the ribs is a thin mix of various acrylic greens I have made during the build, including the dark semi-opaque green from the first attempt.

I'm quite happy with the way the shading looks on the rudder, but less so with the horizontal surfaces. I'll have another go after work tomorrow if I'm not too whipped.
Thanks for looking!
Gaz