I've just started bagging cuttings instead of my usual method of pot rooting. Have about two dozen currently bagged using two different mixes: 1 dozen are in a peat and perlite combo and the 2nd dozen are in a coco coir/perlite mix. Neither batch received any additional moisture. Used plastic sandwich bags (small) and after the cutting was in the mix put a thick twist-tie around the collar of the bag at the top of the medium, folded the rest of the bag around the girth of the cutting with painter's tape then cut a strip of foil and folded that around the tape to fend off any sun rays heating up the tape. Once the mixture was put in the plastic baggy, I cut off the zip or seal strip at the top so that the plastic would fold easier around the cutting. Also trying this with some cuttings with just a few, small emerging roots. Guess I'll find out how it all works out in a month or so!
I can take some photos for you if you are interested and post them. Just let me know.