According to -us/library/windows/hardware/hh450839(v=vs.85).aspx, winusb.h is located in WDK8's Include\um folder, however after installing the WDK8 three times with both the pre-download and download methods, the file isn't there. I'm assuming that by Include\um, they're reffering to C:\Program Files (x86)\Windows Kits\8.0\Include\um. I've also done a search of my system and couldn't find winusb.h anywhere.
Create my_winusb.inf using DeviceInterfaceGUID as described previously. The inf file need to match the VID, PID, and DeviceInterfaceGUID of the USB device. Only Windows 7 and before need install driver.