Well, while Dan does his work for platinum, I don't think thats what
the original poster was inquiring about.  I have done extensive
testing on this and here's what I came up with:
First of all, most if not all film recorders (the things that produce
the B&W neg) are calibrated for TMX film, whith IMHO is the worst film
you culd possible use for this particular process.  So, you will first
need to ask the place doing the output if they will do some testing
for you, or are they stuck on TMX.  If they are stuck, either keep
walking and do searching on labs that will use something other than
TMX or just live with the results you will get with it.
IF you can find a place which will do tests for you, I'd suggest
starting with Berggers 200 speed film, and processing more on the flat
side, i.e. decrease time and agitation from recommended times for that
film.  The other film to test woud be Agfa 100, again, developed a
little flatter than you normally would (but not as much as the
Bergger).
THe point to all this is that the process adds a LOT of extra contrast
to the subject/original, AND TMX especially has a tendency to "band"
the tones, i.e. show distinct breaks in the tonal seperations.
It is a tricky process to get optimum results, and depending on your
needs, expectations, can vary quite a lot.  I always strive for the
best, and know what that is, so I might have too critical of an eye
and opinion, so take what I say with that in mind.

I hope this rambling helps

Alexis

www.alexisneel.com