i was able to test with "sand" today- it works!  The "sand" is sodium bicarbonate blasting media from Harbor Freight Tools- a 50 lb bag was $32 with a 25% off coupon.  It turns out I only need about 25 lbs of the stuff on the table.

I still have to play with it to determine the optimal depth of sand and then test speeds and accelerations.

First test of sand table with sand from Mark Rehorst on Vimeo.