My landlord took out some monitor they had originally left attached to a wall in my rental apartment, and has now left me with a nice decorative set of wall plug holes. Assume for the sake of discussion the wall plugs themselves are gone (it's more complicate but that's the bottom line). The wall is made of concrete blocks cemented together, not drywall. The holes have a diameter of about 5 or 6mm, and a depth of... oh, I guess maybe 2-3.5cm (some holes have a broken-off piece of the plug wedged inside).
I've "filled" holes before, but it has been more of a patching then a filling : When I use a putty knife with some kind of filler material powder, mixed with water and applied - I never get that much material inside the hole, and the mixture kind of caves in, or becomes recessed slightly - try as I might to make several smoothing and get-material-in passes.
I thought about maybe using some kind of syringe-like applicator (which I would need to get); but maybe there's a less half-assed method to do this.