I decided to experiment further with my trial WWII U.S. painting technique, before listening to all of your advice and trying some technique completely new to me.
So here are some 1:300 scale U.S. M18 Hellcats from WWII - another sympathy purchase from eBay, if I remember correctly, so I have no idea who the manufacturer is - which have again been painted with a black primer coat, Howard Hues Olive Drab, some highlights, and an ink wash (but not so strong this time).
(I did, however, use a strong black ink wash in-between the running gear, as I prefer to give the illusion of shadows under the tank.)
(Sometimes I put a black dot on the end of the gun barrel to make it look hollow, but I didn't this time...)
The Hellcat is a tough vehicle to sculpt in this scale, because in real life you'd see the crew in the open-topped turret, and how do you represent that? So these vehicles look like empty tank destroyers...
What do you think? Too dark? Too light? Wrong shade of green? Too much shadowing? Not enough highlighting?