You can see the attachment I use with my old W-300 torch.
The attachment can fit all handle sizes.
One thing that is great is that you can have the roller cam descend onto the lever SSLLOOWWLLY if you want to. When I built my first CNC torch table, I tried a solenoid. Didn't work very well, and it slams the lever too hard. I had to put a piece of urethane foam under it to keep it from slamming.
The stepper motor has a cam with a ball bearing pressed onto it. The stepper just replaces the stepper in your Z Axis. I use a system (Danplot)(I can hear the boo's and hisses now.) that allows me to dictate how many steps the Z Axis travels in a fixed mode, like a plotter. If my motor is 200 steps per rev, I tell it 100 and the cam depresses the lever. If you want to feather or ramp, that works well, also. Ramping helps prevent cold starts.
As you can see, it replaces your thumb on the cutting lever.
If anyone is interested, I can work up a price on these, but feel free to look carefully at the pictures and see if it's anything you are interested in.