Modelling-ABC by Wilfried Eck
The very first of aircraft had their wing structure covered with fabric to create a light lifting surface. Later on also the fuselage got such a covering to reduce drag and give some protection to the fragile structure of wood and wires. As a means of weight reduction even in WW II some aircraft aircraft had fabric covering on ailerons and rudders (some even retaining it for the after part of the fuselage). As fabric covering soaks up water easily it had to be sealed.
The covering was applied by needle and thread and stretched tight. The next step was to apply a layer of cellulose shrinking dope to tighten it further. In at least another layer of clear dope (its shrinking power counteracted by the addition of a proportion of castor oil) the fabric was sealed further. Then followed the actual paint. Naturally there were variations in different nations and times, but the outcome was always the same. The surface was as taut as a drumskin and glass smooth, any trace of the weaving being covered by varnishes.
In models it's therefore complete nonsense to depict a criss-cross "textile structure" the original didn't show. Even if it had, in a model it would be completely out of scale (how near have you to get to see how your tablecloth was made...?)
The other mistake is to let textile covering sag. In reality it was taut, only the ribs and stringers protuding only slightly. See page F, fabric covering
Excluding some types with blunt or even concave trailing edges on wings and control surfaces (i.e. F7U Cutlass) these parts are knife edged.
Contrary so in many plastic kits. Due to manufacturing restrictions most trailing edges in kits are too thick and rounded, especially in 1/72 or smaller scales. But even in larger ones I've seen models with trailing edges scaling to log thickness in the real plane.
To achive this required sharp edge it isn't sufficient to sand the very last part of the surface, the resulting kink making it even worse. To retain a flat profile sanding has to begin further towards the leading edge, the sandpaper being held flat by a suitable piece of wood or plastic (fixing the sandpaper with double sticking tape is no bad idea). Naturally this procedure begins with coarse and ends with very fine sandpaper.
It doesn't matter if during this process the gaps around ailerons and rudders are reduced considerably for they usually are too wide and rounded too. In any case rescribing (with the rear of the pointed edge of a sharp knive) should be done so that the rescribing tool points to the front to create a sharp edge there.