Some tricks is required in order to use

Win32_PerfFormattedData_PerfProc_Process properly, refer to Why Does My Performance Monitoring Script Keep Returning the Same Incorrect Values?

Another post: Getting CPU Usage in a Multiprocessor Machine.

Useful post: WMI Sample in MSDN to remotely target a machine results in an 0x80070005 - Access Denied errorr

WMI tools:WMI Code Creator v1.0, WMIExplorer, WMITester, and WMIReader.