I have 3 walls that are plastered over taracotta block,no board just plaster.what is the best way to get a buckled portion of plaster off in a straight line so as to put up drywall in these spots..Also it may need to be firred up in order to hang the drywall,question is how to attach the firring strips to the taracotta block????These are outside walls(inside the house)should there be some type of a vapor barrier also????? Anyone with knowlege to this step by step process is greatly apprieciated..