Hey Shelia, Good to see you hear.
If they can wait to use the bathroom for about 3 weeks you have to do nothing. Mantovano is a unmodified lime plaster and will go through the carbonization period. If you get wet before this process has ended, you may get some leaching on the lime. Talk to your client and if they cannot allow the plaster to run it's course, you can wax with Cersd`Art. You should wait 3 days before you wax. I prefer no wax myself.
Doyle