would say most buy the precut rockwool made to fit their hydroponic setup if you do decide to cut it up yourself you should probably read up on the procedure as rockwool fibers can be a health hazard.
would also be leary of using any seed from the hermie as you may run into the same problem in future grows but would definetly try to remove all male pollen balls from that plant before they released pollen seeing how you only have 2 plants if you had alot more would probably remove it from the room.