There is no provision for the non-math use of the prime sign. I consulted with Lynnette Taylor on this one and we have agreed that the transcriber has to devise a symbol for this. We suggest dot 4p for the single prime and dote4pp for the double prime. I would follow print for spacing since that is the general practice for symbols of this type.
5e' would look be [simbraille]#e;e@p[/simbraille]
These symbols are listed on the Special Symbols page. If there are only a few instances of this in the print, I would list the special symbols in the text right before they are needed. The concern is that the reader may skip over the special symbols page. But if occurring throughout the book, go right ahead and list on the Special Symbols page as prime and double prime. The text also mentions the symbols, so I'm sure the reader will figure this out.
Thanks for the interesting question.