I had an electrician in who made several large holes (10 inches?)in the plaster walls. The thickness of the remaining plaster is not perfectly even and it's pretty thin right where the holes are - so patching with a piece of drywall is not a good option.
How should I fill these holes? I'll repair the lathe or put some kind of backer in the hole ... but it doesn't seem like filling the hole with joint compound is right... should I use Plaster of Paris? Which will shrink least? Or should I repair the hole as if it were an entire wall - browncoat and topcoat -? I don't know what the browncoat (bottom layer) is. It looks like mortar. What is the mix? (Could I just use vinyl concrete patch and top it with plaster?)