best camera/ flash settings for Lunas?

I am finding Lunas fairly difficult to photograph and would appreciate any tips.  It isn't about under or overexposure (or maybe it is?), but avoiding bringing out any flaws on the wings.  Many times, flaws such as color mottling of the wings, scratches, and other imperfections are showing up in the image.  The scratches can be dealt with in processing software, but the color mottling is especially troublesome to try and eliminate after the fact.  What are some good settings I can try to achieve the most uniform wing coloration, yet giving sufficient detail without emphasizing color mottling imperfections in the wings?  I have already tried various softboxes and diffusers.  For a Polyphemus some weeks back, the softbox did wonders compared to nearly normal speedlight flash, but such a softbox doesn't seem to be helping with the Lunas. 

Thanks in advance for any tips.