i used this stuff.. coal slag
it is agressive enough to kill deep rust and
you can reuse it but it loses its cut the 2nd time thru.
oxide or crushed glass takes too long to do the same job
on deep rust.
you will use up more material to do the same job


plastic media is probably better but its more costly to buy.

http://www.tractorsupply.com/tools/sandb...-50-lb--3905403