I hate to say this... but most of the blemishes on your covering seem to be problems with the underlying structure. I think your covering would be a lot nicer if everything had been sanded with 100, 200, and 320 grit sandpaper before you covered it (and cleaned of all dust, of course).

As to the wing tip and the wing center... I don't even know how I worked around that myself. You just have to work with the covering in as small a section as you can to try and reduce the amount of wrinkles on curved surfaces.

If it's any consolation, the distant shots of the whole wing both look quite nice.