I'm sorry for sidestepping the question, but since I find Spotlight a P.I.A. most of the time, I use Quicksilver for this kind of thing. I have a couple of shared volumes on my network - - I log in to them, tell Quicksilver to catalog them (or any folders on them) and in a relatively short time QS knows every file/folder on them.
You can also limit the number of sub-levels QS will catalog to shorten indexing time, but I set it up to re-catalog every 10 minutes, and after the initial indexing time, I can access anything on these drives pretty much instantaneously.
It has a short learning curve, it's algorithmic AND it's free. I've been using it for years and wouldn't dream of doing without it.