The right-click/set autoshapes default should get you where you need to go
for the basic textbox. It should set font size/color, fill, lines,
linespacing, bullets if you want 'em, etc.
But you can't set the various bullet levels in the textbox. You'll have to
train your users to use the slide layout with the double-bulleted list
placeholders. Or maybe look into Steve and Brian's Shapes/Styles Add-in.
http://www.rdpslides.com/pptools/shapestyles/index.html
Also, after you've set your auto textbox, you'll want to draw an actual
autoshape (rectangle, oval, etc.) and reset its autoshape defaults, too.
Do the following in this order:
1. Right-click the textbox and choose "set autoshape default."
2. Right-click one of the autoshapes and choose "set autoshape default."
It's a little bizarre, but just trust me that you want to set the autoshape
default on the textbox first. Then you want to reset the actual autoshape
default.
Don't *even* ask me how long I mucked about with that one day!