There was a thread on this a few weeks ago. I know that could be said of lots of topics here -- travel shaving, most notably, but the talc thread was pretty long.
I recently purchased a bottle of Newport Talc from Caswell & Massey while on a trip to Florida. The scent is fresh and clean a little goes a long way. It did the trick keeping things dry during those humid FL days.
It is also used for the same purpose that a lady will "powder her nose". . . to take the shine off of the face. It should follow the after shave if a shiny face tends to be a problem.
The barber uses it on his neck brush to help absorb any moisture; thereby assisting in brushing away any loose hairs.