I would let them grow some daughter plants and then cut off the daughters once they've grown a couple of leaves. I've never had good success with dividing a mature plant in half with my crypts, but maybe it may work for you?
They propegate by the roots. There will occure plantlets just besides the motherplants. When you seperate it with part of the root it will grow further making a forest like this. Sometimes broken rootparts will show leaves growing out of them afterwards.