Talc can reduce the shine on a particularly smooth face, as well as hide the shadow that remains even after a good shave. And it definitely can reduce irritation on the neck from your collar if your skin is compromised by your shave.
The only thing I can say about shave talc with any certainty is not to store it nest to your body talc. The menthol isn't at all welcome on the areas I talc after a shower!