Scrape loose paint and paper and apply drywall compound.

What GN says, but use light weight spackle, it dries faster and you will most likely need two coats, sanding between.

I'd use joint compound, applied with a joint knife. I always hated sanding with sandpaper because it's so messy and I hate the way it sounds. Rather than sanding with sandpaper, I use either a piece of fiberglass(?) window screen and/or a damp sponge for smoothing it out after it's dry. Both tricks my Dad taught me. :)

There are no easy to use, cheap products.

Spackle, sand paper, putty knife, cleaning supplies.

What you “seen online” is the same you will read here, this is the same as online.