Question 1, No
Question 2, yes
Basically, if I'm understanding you correctly, you are hoping a sheet of gypsum wrapped in paper is going to pull up bellies in the lathe and plaster.
Trust me it will not.
It was airborne who posted the thread a few years back. As for colouring then experiment with paints and wood stains to get your colours right. Also if
You wanted you could make a latex or silicone mold from old aged timber around knots and speed up the process of forming the knot.
I've seen labourers sent to do test panels on sites where the min price for a house was 300k ( and I'm going back pre 2008) and they have been signed off by the architect and site agent. The brickies could not believe their luck when they saw the standard that was deemed ok.
I've also got an old...
Check all your gutters, down pipes and pointing etc and get a cavity inspection done. It could even be originating from somewhere on your roof or flashings.
I would be surprised if there was nothing stuck in the cavity at those points.