Create the Emitter and the System as shown in the tutorial
Bind an event to the SpawnSystemAtLocation (see below)
Set Location and BeamEnd: Your Sphere as Start/Location and your ForwardVector or the ForwardVector of the camera as your BeamEnd
This way I create 1 traceline when I shoot.
Edit: To alter the duration of your traceline adjust the Lifetime in your emitter (InitializeParticle => Lifetime)