Long, long ago, an old Polish Barber said, " no shame to waste a good soap"
and told me the trick.
After shaving, leave the rest foam in a bowl. She dries.
http://img577.imageshack.us/img577/6178/piana2.jpg
In the next shave just moisten the brush. Again, see the foam.
http://img854.imageshack.us/img854/6438/piana.jpg
The photos are Proraso shaving cream. The effect worse than to use soap.