[caseyhoo]

For CP, as mention by David, bare root. Put it in any plastic bag... normally, I use those transparent. And use rubber band to tight the bag. Make sure there is not much air inside it, so that the plant will not move left and right to plastic beg.

Put the packed CP inside a box and send it.

For aqutic moss, you just need to pack it at any plastic bag as well. make the plant is wet. pack it as mentioned above, put it a padded pastic evolope or box. Then, send it...