ROTFLMAO!!! Good one Bo!
Erik,
It depends on the particular a/c really, and this is where nothing is going to pay off as well as good research depending on the a/c you are wanting to model. Even in WWII, when I'd venture to say almost all a/c were painted with an airgun at the factory, some had hard edge camo, and some had a soft edge.
You'll find some German types in WWI that had a soft edge, but many did not.
Again, you're going to have to narrow the question down to a particular a/c and a particular unit, time, place, etc. as there is NO one answer fits all (or even fits most IMHO) to your question.
HTH, YMMV, FWIW,
Warren