Maybe you are just not using the right keywords when you search? 'Plaster repair skim coat ' brought up numerous tutorials and videos. Don't be totally turned off by mention of drywall because a lot of the technique is the same. We've done plaster repair on several of our walls and it's sort of tedious but not hard.

Google "plaster repair" or "how to repair plaster walls". Lots of tutorials and info. I'm doing the same thing with old lathe and plaster walls. I found a pre-mixed plaster patch at Lowes that works really well. I tried Plaster of Paris first because that was all I could find and it was a disaster. Dries in 6 minutes! What I've discovered is that home improvement stores don't have much in the plaster department because no one builds with that anymore. For serious repair you need a pro. Good luck! I hope this helps.

Java
I had the same issue where paint and the skim coat of plaster basically peeled off the wall to expose the "brown coat" layer. After searching the internet I suspected that incorrectly painted walls (laytex and oil layered on top of each other) and rehydrated calcimine may have been to blame. So i had to scrape and sanded off as much as possible. Then washed the wall in TSP solution. It was then sealed with "gripper" a sealant for masonry found at home depot. Then used a skim coat of joint compound for plaster walls until it was evened out. Texturized it. Primed again. Then paint.

The bad news is that unless you clean off the old plaster there is a good chance anything you do (new) will not bond with the old and then will just fall apart. But if you are willing to give it a good old college try then

take a spatula and test to see how much of the remaining wall is weak/strong enough.

Go to home depot and buy
joint compound,
plaster (dry in a box or bag) AND,
I cant remember the name of it but it is a liquid adhesive made just for this instance but it comes in a pink and black can. The liquid inside IS actually pink.
Buy a 10 inch trowel and a mud tray. buy a 5 gallon bucket to mix the ingredients.
buy a length of wall mesh. It comes in tubes of about 4 feet long. Home D may not have it but you can find it at most industrial contracting stores.

Mix (small amounts) or 1 part compound, to almost 3/4 parts plaster and add the pink stuff (maybe a 1/4 to 1/2 cup at a time and mix it thoroughly. THIS IS IMPORTANT! MIX IT FAST AND START GETTING IT UP ON THE WALL QUICKLY BECAUSE IT WILL DRY OUT AND GET LUMPY.

Transfer the mixture to your mud tray and get a manageable load on the trowel and begin to place it on the wall. I prefer to start working it in along the existing plaster. This process won't be pretty so don't get worried. Try to work fast and get a nice (but fairly thin) skim coat up on the spot you are trying to work with. Once you have covered the entire area with your mix, then roll out the mesh and lay it over the area you are patching (tacky side down). don't worry if it over laps into the old area. Use the flat of your hands or the trowel to gently but thoroughly embed the mesh in to the first skim coat.

Let it dry,(ie: wait a day).

Cut the overlayed edges of the mes off so that they overlap on to the older section of the wall but by not more than a few inches. The mesh has a tacky side. This is the side that should be laid down.

Repeat the mixing and applying until the entire area if filled in and leveled. Feather the mixture over to the old side as well covering the mesh that you overlaid. Just be sure to check for lumps in your mixture (YOU DO NOT WANT THAT). When you are all done let the area dry fully (may take a few days) and then sand it down and it should look great.

Drywall joint topping compound (e.g. "mud") will work fine. You need to get the loose plaster out, then the remaining plaster needs to be made wet. Not damp, wet. Use a sponge. The "MUD" won't stick well to dry plaster, but will stick to wet plaster. The lathe behind the plaster can be made wet as well.

You might also want to try using a primer/base coat that is specifically intended for calcimine/chalk-paint recoating. We've been using BM's Calcimime Recoater 306 (http://www.benjaminmoore.com/en-us/for-architects-and-designers/paint-products/super-spec-alkyd-calcimine-recoater#advs=0&tab=3). I had to call three stores in Seattle before I found some in stock. Otherwise, the minimum order is four gallons. If calcimine or chalk paint also appears on your ceiling, then be prepared for about one gallon per room. The great news is that you can then paint with regular latex on top.

Things to think about: the BM recoater costs about $70/gallon; needs about 3-5 days to completely cure before you can paint over it; if your local BM store has recoater that's been sitting around for a while, then be prepared to wait more like 5-7 days for compete curing.

For best results, definitey follow Hurryupthecakes' advice and wash well with TSP first!