I've found that white wash remains water soluble until the lime has cure (reverted to lime stone. As this can take a few weeks, I would try it out doors during the dry season. Living in Missouri, USA, I understand how tricky that could be. I've also noticed that while it will rub off if, you bump against it, during that time. Once cured it's very durable and resistant to abrasion, in some areas where I neglected clean up, it became impervious to moisture, scrubbing, and mild acids.
