Sanding latex paint is a futile attempt at smoothing. Better to skim coat a little drywall compound over the area and then sand with a sanding block. After sanding , run a well dampened block sponge along the area where the patching meets the old wall area. This will get rid of an minor ridge of compound.

You will want to prime this new patch, but use an old, worn roller in order to impart a slight texture, as your new patch will probably be noticeably smoother than the old roller texture on the wall. Further, I would give the new patch a quick, light coat of the finish coat paint, followed by a general painting of the room. Should a "flashing" of the patch still be visible, you may be forced to apply a second general finish coat.

Cannot argue with that^^ advise.

And your advice is...?

My advice does assume that the homeowner's house has smooth wall, rather than texture. If it is textured, similar advice is still given, but a final general texturing of the wall would mask any old imperfections. I grew up in Chicago, smooth wall country, and now live in texture country, the Pacific North-West.

I recently prepped and painted a bathroom that had a series of paint flaws - drips, various thicknesses of paint due to paint-arounds of items later removed, and some general flaws. I used my Dremel multi-max with the sanding attachment to remove the bumps and smooth out the paint where needed. I skim coated only in areas where it was needed, then primed with oil primer, then painted.

graywings, you certainly can knock down the high spots to lessen the amount of skim coating necessary, but normally, latex paint sands very poorly.

And your advice is...? same as yours, that's why I did not argue :)

I would try an orbital sander before skimcoating, but it really depends on the texture.

Getting rid of surface ridges and texture is always a problem, even on smooth wall. I always make aware customers who want to tape off stripes on their walls, that a few years down the road, they are going to have a real problem getting rid of those slight 3 or 4 mm ridges left at the taped edge. Where you try to skim coat the edge of the ridge, you end up with a super smooth band in the middle of years of roller texture. And again, ridges just don't sand off of latex paint. In the worst case scenario, the whole wall might have to be skim coated, or, in the case of textured walls, the whole wall might have to be re-textured.