In the past I’ve used a retractable sharpie wrapped in electrical tape to the correct diameter to fit the torch holder.
THC off.
Now I just use the DRY RUN option in fire control if I am not confident with my set up.
Good idea.
I wonder if the retractable sharpie could be gut out and loaded with a spring? then use a standard sharpie cap to keep iit from drying out.