>>538064626
with the maps like this, i pick the larger open area and drop on the edge of it and drive to the other end, it works pretty well and i get a few drops reliably in a minute or two
if both open areas are about the same size, it can be worth it to drive around the edge of the map to get to the other side and you might be a couple more drops
the normal open maps still work fine though so don't obsess over trying to select the cave ones every time

>>538065061
i just got done farming a few hours ago
for the most part i would get 3-5 drops per map, but near the end i had 3 missions in a row with zero credits, but then it quickly went back to normal after that
just keep going