This is a quick view of how I trim the foot on a tall narrow necked vase.
To get the piece supported well enough to apply the pressure needed to make my cuts, I throw a thick walled trimming chuck to hold the inverted piece steady. I try to let the fresh chuck set up for a few hours before using it. When I'm ready, I simply invert the vase into the opening of the chuck, level and center the ware and start trimming.
The leather hard chucks are reusable. I simply leave it on it's throwing bat and bag it up well to keep it at a leather hard state. I try to set-up my work scedual to make use of a freash trimming chuck. I cut freash stencils, gather supplies, and throw as much work as I can juggle to finish without loosing control, (not often easy with 2 kids).
Once I'm finally finished using a trimming chuck, it's left to dry out and broken up and put in my bucket of clay scrap for recycling.