Small chunks... Use a grater
i.e. use your man grater.

If you wet your whiskers then rub the chunk on
your face you will transfer/ grate more than enough
soap to face lather.

You can also hold them in your hand
and work a brush on them to get a
lather going.

When they get too small for that toss them in
the bottom of a mug with just enough water
to get them soft enough so they stick to the bottom.

If they are really fragrant you can toss them on
top of a mild inexpensive soap like Williams or better
on top of one of the fragrance free hypo allergenic pucks that
some of the sites we talk about have.