Patching and Plastering - "Skim Coat" tool marks,dings/dents in plaster

I just bought a house, which was made in the 1940's, and removed all the old wallpaper using a steamer. Once all the wallpaper was off, there was residue from the left over adhesive/paper backing on the plaster; makes the walls feel gritty. I'm planning to sand the walls down to leave a smooth finish. But there's a few things wrong with the walls that I want to correct before paint goes on.

1) While removing the old wallpaper, i put in a few tool marks from the 4" putty knife while scraping, nothing to deep.

2) I have one or two hair-line cracks running up a few walls. They start at the floor and go about 4ft. up. Where the cracks are, the wall doesn't bow/flex/flake, seems pretty sound.

3) And then there's the usual dents/dings from everyday living.

So, my question is, after sanding the walls smooth, should i prime the walls with a latex primer such as Zinsser and then use pre-mixed joint compound to fill in all the imperfections? Or do I have to use plaster to fix the imperfections?

I rather not skim coat the entire wall, being that I'm a virgin when it comes to working plaster.

Thanks in advance!
-mark:D

I am not an expert but I think you have a good plan. I did the same on my old house and I have had no problems with it.

As long as the areas to be repaired aren't chalky or dusty you can skip the primer before applying j/c. There are 2 ways to fix the settlement crack. tape and mud it like you would for drywall or etch out the crack and fill with durabond. You could substitute j/c but the crack might reappear later.