Creating large amounts of starter

So far I've just been baking small batches of bread.  Ususally 2-3
loaves on a weekend or so.  I was thinking about what it would take to
make a much larger batch of dough at once and am curious how to do
that.  It's pretty easy to build 2 pounds of starter in a bowl, but if
I wanted to build 20 pounds of starter how do I go about that?  Do I
mix it in a 5 gallon bucket?  Or is a 5 gallon bucket too small?  I
recently aquired a 20 quart mixer, do I mix up/feed the starter using
the mixer (using a whisk) than dump it into a bucket?  I'm sure some
of you out there have done this working in bakeries.  I'd love to hear
your advice or the method that was used.

Anton