Heres a REAL way to get Combo points with sap (PVP only):
Sap your PvP target, and then cheap shot him while spinning away from him in a manner that your cheap shot lands, but your autoattack isnt facing the right way to break the sap;
You will have a target with both sap and cheap shot active, and have gained 2-3 combo points.
You can now restealth and reopen with whatever opener you want and have full CPs.
Enjoy. And yes, this trick is OOOOLD ive been using it since Vanilla