the type of repair solution was my specialty when I had owned my painting company. Here is the best way to repair your walls.
Scrape all the loose paint around the bare plaster completely off. Next, carve lines crisscrossing the bare plaster in a grid pattern-don't worry about making the lines too deep. This will prepare the surface to accept filler material and will also help keep it in place while it is being sanded and after it has been painted.
To fill the area, use joint compound and not spackling (I had never used the stuff as it is almost impossible to shape ande finish. Make certain to use the type of joint compound with the adhesive mixed in (green lid not light blue).
When you sand the surface it is ok to use a heavy grit sandpaper like 60 or 80 but you must be prepared to add another coat. Keep in mind that this process is very dusty so cover whatever you don't want to have exposed to dust.
When you have finally coated and recoated the areas you have repaired, check for consistincy with your bare hand (a flashlight at an angle in the dark will show you imperfections like airbubbles).
Make sure that once you are done with the repair that you prime using one light coat at first then one heavy coat(DO NOT DOUBLE ROLL OVER ANY AREA WHILE IT IS STILL WET-the suction from the roller cover will pull the patch out and ruin your repair).
Lastly, you may have to sand or all of the adjacent "orange peel" or be creative with a heavy nap roller cover so that your repair looks consistent with the the rest of the surface.