I would like to know if it is possible to add a separate handbrake. I have everything from Fanatec except the handbrake. I can't figure out how to add a separate handbrake as I take both as a separate wheel.
I've tried it with a mouse, but haven't tried it with a separate handbrake. You can change the handbrake from button to axis in options -> controls. If you use the handbrake with a wheel, it should be almost plug-and-play. If you use it without a wheel, you need a "Fanatec ClubSport USB Adapter" which converts the handbrake cable into USB. I've attached a sample screenshot, you should have more "Available Axis" on the right side, one of them will be the handbrake.
It should work without any problems as long as each device is a joystick on its own. Are you looking to make a DIY handbrake? You can use arduino proMicro to be your joystick interface. Let me know if you need to know more about how to make one.