I'm sorry, but I found your message only few minutes ago.
Personally I don't have any suggestion.
By the way, I'm not interested in material collected in Malaise traps, beacuse it's really impossible to prepare it. So I always refuse specimens collected with this kind of trap.
Often the cuticula is too much dehydrated and the dehydration cause many problems. The dehydrated cuticula can modify the anal margin and the relative position of the anal teeth, which is very important in some species groups (i.e. ignita group). Moreover, it's basically impossible to extract the dehydrated male genitalia, because you'll always break them.
In case of specimens collected with yellow pan traps is usually easier. I prepare them with pins, exactly as Coleoptera.