I've now sent out all of the pawpaw seeds and almost all of the folks that got them asked about propagation. Here's how we do it:
1 gallon size nursery pot - the roots get impressively long and need the space
potting soil, seeds and perlite or something similar.
Pics are attached - we water them in, once it's potted and leave the pots outside. In Southern VA, we get snow, ice etc as well as "0" degree temps in the winter.
BE PATIENT!!! We don't see sprouts until early July here. Once sprouts are about 3" up, we carefully empty the pot and move each sprout to their own 1 gallon pot.