I have a supply of theatrical neutral density gel in my studio flash kit.
With a pack and head rig in some situations you can't always just dial back one head, and you don't always want to pull back with certain light modifiers, so a bit of ND across part or all of the tube output is the cats meow for that situation.

I folded a couple of thicknesses of ND9, ie a three stop neutral density a few times back onto itself until the digithing I was using to meter on the fly started to show a reasonable exposure solution.

I know multiple acetate filters are not the prefered optical solution, but the results from the digi via the occular of one side of a pair of binoculars yielded a pretty good image. I have yet to process the film I shot.