I always ferment my earthen plasters. It smoothes out the mix, makes it stickier, easier to apply and more resilient and resistant to damage (of all kinds).
When mixing up a batch, weather using horse (or cow) manure, straw, rice hulls, shredded
newspaper, etc., I'll let it set for a few days until the mix smells like a beer wart. If it sits too long it'll smell like sewage which is unpleasant to work with. Natural enzymes will go to work on the organic material(s) in the mix, slightly breaking down the straw (or rice hulls, manure etc.), releasing lignins, mucilage and various other gluey substances.
Sometimes, if I have some lead time, like several months, I'll whip up some clay slip, screen out the rocks and add a handful of manure or chopped straw, manure is better. This won't be the final mix, which will have MUCH more straw/manure/whatever, it's just adding a little food and inoculating the batch with enzymes. I'll then whip the batch with a paddle mixer every so often and let turn into a thriving community of glop. When the time is near to use the stuff, I'll add the rest of the final mix in and let sit for a couple days (depending on temperature). This way of doing it typically does smell pretty rough and it's more suitable for exterior applications.. It makes for a damn fine finish!
NEVER use cementitious stucco on earthen walls! Lime is fine, (portland) cement is not.
All over the world in the last century, it was thought that one way to protect ancient earthen buildings was to stucco them.. Now, it turns out that stucco is the NUMBER ONE destroyer of those same buildings. DON'T DO IT!
Cement is hydrophilic, it wicks and sweats moisture, it also becomes a condensation point for water vapour moving through walls. Part of the problem is that since stucco is fairly resilient, you don't see the damage underneath until it's MAJOR.
but they where waiting to start until "the rice husk cob had fermented" before using it 
