I've got a job to start today, but i whent to talk to the guy last night, and check the walls out again since the wall paper has been removed. the walls are quite bad with loose plaster and channels cut out for new shower pipes 7 wires. so im going to dot n dab it all. but my question is do i have to screw the plaster board to wall as well as dot n dab compound. also where do i get the dot n dab compound.