The JPF is easily divided, since it spreads by rhizones, you can remove a section of the rhizome (with a frond or growth bud) using a sharp knife or shovel. The Autumn Fern is a little more difficult, since it has a woody crown. Slice off a portion, with a frond(s) and some healthy roots with a knife or shovel. Pot the divisions in a moisture retentive potting mix and keep moist, in total shade, until they appear to be growing normally.
The big box stores near me stock both of these during the growing season and have seen small pots there for $3-4. There is an Autumn Fern cultivar 'Brilliance',now available,
that retains the bronze color well into the late spring-early summer. Have seen those at the box stores, also.
Rb