Usage patterns
〈事〉のコツをつかむto get the hang of (doing) something
After practicing many times, I got the hang of riding a bike.
骨を拾うto gather the bones (from the ashes after cremation)
The relatives gathered the bones at the crematorium.
〈人〉にコツを教えるto teach someone the trick/know-how
The teacher showed me the trick to using a kitchen knife.
〈事〉にはコツがあるthere is a knack to (doing) something
There's a trick to operating this machine.
Expressions
一将功成って万骨枯るthousands die to make one hero; one general reaches glory, ten thousand bones are left to dry