Either are fine, they just give different final finishes. Walnut is a touch more aggressive, corncob gives a touch more shine, both are excellent choices.

Just make sure to get real tumbling media if you use corncob, cutting corners and getting stuff with different grit size can be hit or miss. Supposedly you can get walnut shells for real cheap from pet places.

-Hans

Just make sure if you get the corncob at a pet store to get the very fine grain stuff, if they have it. Usually it's just too big, and won't get into tight areas as well.

I'm going to give a couple other things a try in my own, I've heard that using silica sand works well, and I have a lot of glass bead to try too.

-Hans

No worries really. Some pet stuff is great, some isn't. Having that initial "sample" to look for in the future really helps, as now you know what grain size you're looking for.

-Hans