The short answer is it is not going to work.
To make a vibratory tumbler work with steel shot requires that
the tumbler be loaded at least three fourths full of shot. That means
that you need about 30 pounds of shot. Stainless shot goes for about
$150 for 10 pounds. Running less shot will just jiggle rather than
roll and result in your work pieces having little trails marked by
Shot must be run wet to make it move.
While you might be able to run wet media in this as a closed
system, not flow-thru, the tumbler won’t move the shot enough to make
it do work.
If you try all this, you will likely ruin the tumbler - it simply
isn’t strong enough.
You could buy ceramic bead media and make it work in your tumbler -
it is light weight and runs nicely in a closed wet system. Buy at
least two sizes of beads.
Or buy a little rotary tumbler and a couple of pounds of shot.
Or for a really cheap deal - put about 2 pounds of shot in a jar
with water, soap and ammonia, and spend a day hand turning it. You
need to turn it end to end because just rotating it around the
vertical axis will have the shot just slip around inside the jar.
The last thought is that steel is for burnishing, to clean the
pieces, you probably want to run some abrasive media first.