Is it O.K. to clean 2 or more calibers of brass at the same time?
Say, .308 with .45 LC?

And do you prefer to clean brass before or after resizing and pushing out primer? I can make an argument for both. I know guys that do it both ways and all have their arguments. I've tried it both ways and seem to prefer cleaning before. Oh yeah, I use a tumbler with corn and polish.

I tumble several different calibers together. The only problem I've had is with some large caliber pistol brass sometimes the casing will slide over the rifle brass and that spot won't get cleaned. So if this can't happen, then I tumble it together.

As for before and after, I tumbled them before resizing so that dirt and grit doesn't get into my resizing dies, and I then throw them in there again after resizing to remove the lube.

I mix my brass when tumbling. Smaller cases can and will slide into larger ones. I tumble both before and after sizing. The problem with tumbling after sizing is that media can get in the flash hole. I normally put a decapping die in the press and pop out the media, beats digging it out.

I had this problem, but switched to 20/40 grit media and it works great and no longer sticks in the flash holes. After switching, I don't think I could go back. Now I don't have to worry about it.

mixed, before sizing and after decapping. i always clean prior to sizing so that i can sort through and find what brass has pressure marks, potential case failures, etc. i use corn cob media, then ground walnut. in the corn cob, a touch of jeweler's rouge, because it shines the brass in a way that makes the marks easier to see, at least to me. it doesn't do much good to resize something you're going to throw away, after all.

I mix brass to an extent. I dont tumble 40 and 45acp at the same time, or 9mm and 40 at the same time. Causes major headaches!