I'm glad you're enjoying the Boku Undo colors. Another way to protect the
finish of marbled papers and keep them from rubbing or chalking is to spray
them with a fixitive like Krylon or Blair workable matte fixative. The
product is used by pastel and watercolor artists to protect artwork from
smudging. I can't vouch for its being archival and it is noxious and should
be used with a mask or outdoors. But it does dry clear and protects work
nicely. It may also give your rice paper a better finish for origami folding.
I can spray a piece of the paper and send you a sample if you want to try it.