Hi,
yeah, you need one raycast per controller, this way both will act as a "Mouse over" on interactive elements in your world. and it solves the problem of knowing which controller is pointing over when there is a controller action.
on the ecosystem there is two samples that you should check out:
GetNextRaycastAllHit and RaycastHitNormal they will show you a lot of what you need to do for your case. Extrapolate that the turret in these two samples are one controller.
Bye,
Jean