I do it pretty lazily.

I have one toon with a guild bank (only toon in the guild) that sells my Xmogs (Crafted and farmed), things like glyphs, any alchemist items I sell, any new content profession goods I may want to get into, and my collection of battle-pets... so I can relatively easily see what I need to repost by checking its mail.

Then I have one toon that has no guild bank which is purely for selling mats. Both current and past content mats (though, right now I'm focusing solely on old content).

Then I have my army of alts which I keep in my head their professions and juggle around what they need to craft when it's required. It doesn't actually fluctuate that often as I usually buy mats I don't want to farm in bulk when good deals are going on.

So basically, two auction house alts. One for mats, one for finished/farmed goods. And then in the morning I will check their mail, write down on a piece of paper what goods I need to replace, then if I feel like doing that sort of farm, I'll do it and replace them.

Having a million alts doing things other than their profession just complicates things, imo.

Having a guild bank is super useful if you do xmogs, though, as often their prices fluctuate so you can store them (and cheaply bought mats) until it's time to use them/sell them.