I am afraid that you need to do more research/study before you ask this question.
The concept of CoS is pretty much the same on all junos all across different platforms, including M/MX/T/ACX/EX/QFX/SRX. But the syntax can be different. If you well understand concept of classification / scheduler / policer / rewrite / shape, I believe you won't get distracted by any "rumor". Because, at the end of the day, CoS is pretty simple from configuration perspective.
However, CoS is very platform dependant. On what platform are you trying to implement CoS? For example on MX. It may also depend on the type of card if you are using complicated technologies like ingress in queueing, hierachy scheduler. Otherwise, it's pretty common.
I'd suggest you to find some example on Tech Pub based on what platform you are using to implement CoS (Most of them should be working for recent junos, eg 15.1 later), if any specific error pops up, we can look into it.