First off slings are awesome fun.
The trainer though is a bit problematic. The other night I spent 50 minutes and 7 rations chasing him down. Finally I did a peer zigzag acrossed the area and found him, but really that isn't much fun and kinda strikes me as metagamish. By the time I found him all I wanted was a lesson and to log off.
Smaller area? Apparent tracks? Trail of manure? Tips?
Love the skill but it has me questioning its worth and play value.