Oh dear, Dallasbill...I just saw this post because chiefneil was kind enough to link to the thread on another forum. Thank you so much for posting the pics and linking to more. Your house takes my breath away. That is the *perfect* wall treatment for the design of the home. That last picture of the several planes of wall with the different inflections of the finish...calls to mind Georgia O'Keefe for some reason, that same stillness... Going back to look at it again and sigh.

really not clear in your post if you have orange peel or not and if you are wanting this done to all 4000 sq ft Nevertheless, venetian plaster is finished with a glass like appearance and smooth as silk. One really needs a true smooth wall finish (preferably-level 5) because it will show every imperfection in ones walls, if not. If you have orange peel, (which I really didn't understand a yes or no), just trying to use VP and fill in to get to a smooth finish will be out the wazooo in cost. Synthetic plasters will be cheaper than your true lime based plasters. Which ever you use, expect lots of work, (arm work) layers, and lots of cost.

I would purchase a clear glaze to protect the finish. This will give you some washability to the surface and would provide a satin finish over the plaster.

Venetian plaster looks awesome when done correctly, but it is EXTREMELY difficult to do. I worked at Home Depot for 11 years and worked with it many times. It is basically a lighter version of drywall that is tinted to a color. You trowel it on, let it dry, sand it, trowel on another coat, let it dry and sand it again...it ends up looking like a two-toned faux finish, kind of marbled. The key to sanding it, or burnishing it, is that it gets shiny. Paint sales representatives tell you that it's easy to do, but they show you how on a small board instead of a whole wall. It's actually back-breaking work to do a whole room, and it takes several gallons to complete a job. Retail cost of it is fairly expensive too, at $30-$50 per gallon. You can paint over it later, and you might see the Venetian plaster/texture underneath, it depends on how heavy you troweled it on, and how much you sanded it. Honestly? I used it myself at home to do an entire hallway, and I wouldn't put that torture on ANYONE else! It's not an easy job at all. Hope this helps!