This, I believe, most of outdoor people once in a while do have to deal with rashes between thighs, around the groin. This may really screw the entire trip and make it annoyingly miserable to walk any further.
  
The best that I thought I can do to avoid them is, I apply coconut oil before starting.
But when you trek through waterfalls or cross streams, this habit doesn't work. And, after that when I sustain such rashes, there is hardly anything that I can do.

Still, what can be done?
What should be done to avoid them? And, what I can do to suffer less anyway if I sustain that thing?