Hi Alice. 

Yes.  I have actually carved papier mache by several means as follows:

Exacto knife
Sand Paper
Tooth Picks
Skewers

Sculpting includes pressing and forming.  Carving is another form unto itself, though it can be incorporated into sculptures such as stone or wood, etc.  Wet sculpture is hand formed in its raw stages; though can be assisted by different tools.  Such is the case with clay. 

The wonderful qualities of dry mache sculpture can allow the surface to be whittled or carved from some forms of pulp which are tightly packed and softly adhered.  That is to say, sticking to itself enough to allow for cutting without pulverizing the papier mache.

Liquid starch allows for that with closely packed pulp.  Proper care and selection of tools is always the consideration.  Some glues and adhesives do not allow for this.  It then becomes a matter of experimentation to see which works best for your project.

If you want to practice, just make a huge lump and begin to whittle.  If it falls apart, try sandpaper.  If that falls apart, try another type of adhesive or perhaps paperclay.

Hope this helps.

Rozani