So far we survive without drones but they are on the shopping list
You can achieve quite a lot with tall monopod and wireless trigger.
As for overlap:
- I tend to shoot for too much overlap rather than too little,
- I try to be really aware of what each photo captures, memorize features and make sure they end up in next frame
- I am really methodical about moving along captured geometry. I try to shoot in rows, I tend not to get distracted with cavities (and such) that require additional photos, I get back to those later.
- I try not to shoot multiple camera angles from same position, it's better to just move your (camera's) position
Hope that helps!