Quote Originally Posted by wiseowl
1. How effective at reducing the harshness of shadows are the metz bounce attachments? (A bracket which attaches to the flash and holds a card.) Or any other suggestions.
It does help. Two things to watch are:
The card can fall out! Play with it before hand - a few subtle bends of the clips should sort it out.
It uses a LOT more power. Make sure you've got a couple of spare battery packs, and watch your cycle times - the flash takes a LOT longer to charge, so if you're rushing it can fail to go off for some shots.

Less effective, but less troublesome, theres Metz also make a diffuser, which just clips over the front, and softens the flash a little.

Quote Originally Posted by wiseowl
2.Any suggestions as to how I can effectively use flash to light a group of 80 people? I have at my disposal 2 metz 45-ct1's and a vivitar 385.
With 400 film a metz should be able to handle it easily (that would give it a guide of 90, so at f/8 it goes 11 Meters!). It's not pretty/artistic/studio lighting, but it's never going to be - you just need to make sure it's decently exposed. A bigger problem is getting everyone in - make sure you've got a reasonably wide angle lens, and stand on something to get up as high as possible (if necessary take a step-ladder!) so you can group everyone in close.