Thank you for the comments everyone - the technique is quite simple (it must be, if I can do it) and is aimed at replicating the finish I see on aircraft in museums where the material appears glossier where stretched.
In my model, I think the contrast between the ribs and the spaces is perhaps overdone, and may be toned down with a coat of Klear, but I am tempted to leave well alone. The hardest part is getting the tape I used (Bob's strippers - 1mm width) not to pull up the decals, even though they had been previously sealed with klear. I had a few mishaps, but managed to save the minor tears and patch up with the original decal. The undersides in CDL will get a bit of shading/weathering to further highlight the ribs and edges, but not too much, I want this model to have an "almost new" appearance.
I have found that buffing up the wings (like polishing shoes), after the main colour is painted, will highlight the raised parts such as ribs etc whilst leaving the remaining material a slightly uneven satin finish. The uneven-ness can give a bit of variation and texture, rather than stark and completely even painted surfaces. I would ideally then leave the wings alone, but the decals then are too glossy, hence the klear/tape/satin varnish process. The solution to that would be to paint the national markings instead of decals, but that is another problem altogether.....
