If you can swing it, I would seriously consider investing in a bigger
mixer. It would save you lots and lots of heartache. If this is a long term
contract, it maybe worth the expense. Especially since you'll end up with 2
mixers, always better than one.
A few more tips:
1. Timers are your friends. I work with about 4 timers (and that's not
including the timer on the 2 ovens I have to manage at the same time). I
use these to keep track of proofing and mixing times.
Write out complete lists of every task that needs to be done. Then
prioritize (spelling?) that list. I usually do so according to what takes
the longest amount of time (usually what takes the longest to proof needs
to be done first), and then what has to be done first or immediately to
complete later tasks. Make good use of notepads!
Mise en place has to be the rule in a high volume production scene. Before
you start mixing and baking. Have everything ready: equipment gathered and
organized, all ingredients weighed and/or measured.
Train yourself to be multi-tasked. This is easy when you've got more than 1
mixer. But if you've got a food processor, you can utilize that for some
kneading tasks. My rule of them is that when you've got one thing going,
start on something else. When one gets good at this, it's rather amazing
what can be accomplished in a few hours.
Clean as you go. Very important.
Make sure you are well rested and well fed before you begin. You can run
out of steam fast if you're starving or sleep deprived.
Hope this helps :)
Roxanne