Just thought I'd add my two cents.
1) the bigger and harder the media the coarser
2) polish is the key to cleaning. I add polish everytime
3) When adding polish let tumbler run till all polish is mixed in, no clumps.
4) Don't leave the top off when mixing the polish, drys out the polish, talk about dust.
Almost all corncob media comes from the same mill in Mt Pulaski IL. www.mtpulski.com
I've been getting mine from them for years and when I first started getting it I told them I want the same
stuff MidwayUSA gets. (14/20) I pickup bags (50lbs) for $16 (include tx)