Wall Prep on Unfinished Plaster

...at least I think that's what it is. Total amateur here, just bought my first house (pre-1900 colonial), and as my first project I want to strip the hideous wallpaper in the living room and redo the walls with fresh paint.

I did my reading and Youtubing, but once I started actually taking a section of wallpaper down today, nothing seemed to line up with what I was expecting. The wallpaper itself came off fairly easy, all in long strips except right along the trim. However underneath it I was surprised to realize that the walls appear to be unfinished. Given the age of the house and what little knowledge I've gleamed, I believe they are horsehair plaster. Here are pictures for clarity: Album

So here are my questions:

- What kind of prep do I need to do before painting? Everything says to clean the walls thoroughly with water, but I'm not sure if that applies to unfinished walls or not.

- What are the white spots on the walls? Initially I figured they were joint compound, but it is all over the walls. I sprayed some hot water on the wall to get some stubborn pieces of the backing sheet off and scraped with a putty knife if seemed like they were melting off the wall... is it wallpaper glue from the backing?

- I bought several gallons of Sherman Williams/HGTV Ovation Paint + Primer during the recent sale at Lowes (they were out of Valspar which had better reviews), should I still prime the walls separately first?

I'd appreciate any input or tips anyone with more expertise could give.

 

Chop out whatever is loose. Fill the holes with joint compound. Use joint compound, to cover any other rough spots. Let it set over night. Sand or use a sponge, to make it smooth. Then prime & paint.

 

I'd use either Zinnser's Gardz or an oil base primer! That will bind any wallpaper adhesive that didn't get removed. Failure to either seal or completely remove all the adhesive often results in a motley looking finish because of the reaction with the latex paint/primer and the adhesive.