On way that was suggested to me was to remove them from the pots, shake as much dirt as you can from the root ball and then put into large plastic trash bags. Do not tie the bags shut. That way you should be able to just set them on a table or something and stack the bags up. Someone please correct me if I'm wrong in doing it this way.
I'd also suggest you go over to the Plumeria 2019 or the Plumeria forum and ask there.
