I have used a "cradle" or sling cut from fiberglass screening to support
very thin paper. Cut the piece longer than the paper so it will extend on
both ends for handling. The wet paper clings to the screen and can be
lifted easily from bath to bath. This is no use for gum, where you want
to put the paper in face down, but should work well with platinum which is
done, as I recall, face up.
Remove the paper from the fiberglas before it's fully dry to avoid screen
marks.
Judy