This leakiness happens to me too, and I would bet that it's pretty common. I'm rather sensitive in that area, but may people may not even notice it.
For me, it really depends on the consistency of the preceding movement. Well-defined solid movements usually don't require any 2nd cleanup, but soft or runny movements almost always do. Most days just require a single extra cleanup, which I usually do in the evening or before bed. Some days there's no leakage at all. And other days require multiple extra cleanups. I can "feel" when that area needs attention.
I've just assumed it was part of getting older, and having a job where I sit too much. But it may also be partly due to more awareness of my body as I age. As for solutions, the usual suspects are probably your best bet: Healthy diet with lots of fiber, exercise, and less sitting.
Well, not sure. Perhaps the first time, you could try a wet product made for wiping (but do NOT flush them, throw the away). This will get it all, most likely. You probably have a bit dried or in creases, etc. and when you sweat a bit, it mingles with that and is more runny and gets on your underwear or comes off easier when you wipe. That's my best advice.