I am prepping 100 year old plaster walls for paint. At first I assumed that they were plaster and lathe, but they are actually some type of cement board with a lime (I think) plaster veneer. There is some light surface cracking at the joints and peeling paint throughout. Does the following sound right: Scrape the peeling areas and open the cracks a bit. (Should I tape these seems, if so what is recommended) Apply a bonding agent to these areas and follow with setting compound and then all purpose and prime everything with USG First Coat to even it all out. I appreciate your help.