Success!
I've done this, as have many others.I agree with the above, you don't need any sort of special filters. Use a matte black backdrop, and save a little of the fabric to cover the chair or bench you're using.
Film has a limited latitude, usually only about 3 and a half stops right? What that means is that any object that shows up middle grey at any particular light level, is going to all but disappear with 3 and a half stops less light reflecting from it.
So, using your handheld light meter as as spotmeter, measure the light on your model so she is at least 4-5 stops less exposed than the fabric.
Voila, invisible background + backdrop.
MISTAKES I MADE (and things I should have thought of):
I'm poor so when I went to the fabric store I bought the cheapest fabric they had, black broadcloth for about $3.50 a yard and my huge backdrop only came to about 50 bucks with lots left over to cover the chair. Unfortunately I hang it against a picture window, and the broadcloth is thin so it allows light through during the day and spoils the effect. I can only use it at night.
When I hung my backdrop, there were deep folds in it, and in one or two places where the fabric curled outward toward me, on one of the photos I could almost make out a tiny bit of texture in the background. I burned it in, and it didn't show up on the final print though.
Also, I wish I had lit the models hair a bit better from behind. Her hair was bright red but even Panchromatic black and white is less sensitive to reds than to blues, and it showed up really dark on the film, almost disappearing.
Also, I overexposed a bit, because I didn't trust the readings my "then new" handheld meter was giving me, and a bit of fabric around the models chairs arms was visible making more burning for me. Next time I'll underexpose by half a stop or a full stop and deal with the thin negs, that should work better.