Yes they can help but my experience shows that TD works better. Bentonite clay is great to add to shaving soap for slip. Because clays draw out impurities in our skin, be careful because they can cause a soap to be too drying for some.
I use a fine bentonite clay powder. It does not turn the soap any unsusual color - the clay itself is gray, but you can still color the soap whatever you want. It does draw out impurities and provide great slip for shaving soap, but I have seen people use it in any kind of soap. It can dry the skin a little, which is why I superfat my bars that have clay in them. I use 1 Tbsp. of clay per pound of soap. A great place to get it at a good price is www.bulkherbstore.com