Drywall repair is three different jobs depending on diameter. Match the method to the hole and each one is genuinely easy - the skill is in thin coats and patient sanding, not in the patch.
Riley Brand
For anything up to about a centimeter - nail holes, anchor holes, picture-hook damage - lightweight spackle is the whole job. Press it in with a putty knife held at a low angle, scrape flush in one pass, and walk away. It dries in 30 to 60 minutes (many spackles go on pink and dry white as a built-in timer).
Slightly overfill, because spackle shrinks as it dries, then sand smooth with fine-grit paper (180 to 220) in a few light strokes. Wipe the dust off with a barely damp cloth before painting - paint over dust peels. For deep anchor holes, two thin applications beat one thick plug that cracks as it cures.
For holes from 2 to 15 centimeters, use a self-adhesive mesh patch - an aluminum-centered sticky screen sold in sizes. Trim any loose paper around the hole, stick the patch centered over it, and skim joint compound over the whole thing with a wide (15cm/6-inch) drywall knife, feathering the edges out well past the patch.
The technique that separates invisible repairs from lumps: multiple thin coats, not one thick one. Let each coat dry fully (overnight for joint compound), sand lightly, and add the next coat slightly wider than the last - three coats, each feathered further out, ends in a patch you cannot find by hand. Thick single coats crack, sag, and telegraph through paint forever.
Above 15 centimeters, you need actual drywall. Cut a scrap piece about 5cm larger than the hole in both directions, then on its back score and snap away the gypsum border - leaving the front paper attached as a 2.5cm flange all around. Square up the wall hole to match the gypsum core, butter the paper flange with compound, and press the patch in: the plug fills the hole, the paper flange becomes its own tape.
Skim, feather, dry, sand, repeat - same as the mesh patch. For holes bigger than roughly 20cm, or anything near switches and pipes, the proper repair is screwing a drywall offcut to backing strips inside the wall; and before cutting drywall anywhere, check what is behind it. Cables and pipes run vertically from outlets and taps - never cut blind directly above or beside either.
Sand with a light touch and raking light - hold a torch or work lamp at a sharp angle across the wall and every ridge and dip shows. The patch is done when raking light reveals nothing. A sanding sponge follows slight wall curves better than a flat block.
If the wall has texture (orange peel, knockdown), a smooth patch will show even under perfect paint. Spray-can texture in both styles is sold at hardware stores - practice on cardboard first, mist it on lighter than you think, and knock down with a wide knife if matching knockdown. Texture matching is the genuinely fiddly part of drywall repair; smooth walls are the easy mode.
Prime the patch first - one coat of any wall primer, or the compound will drink paint and leave a dull 'flashing' spot visible at an angle. Then paint the patch and a wider area around it, feathering the edges with a nearly-dry roller.
The honest truth about touch-up paint: even the original can, years later, will not match perfectly - paint on the wall has aged and faded. For small patches in low-traffic spots, close is fine. For a large patch in a prominent wall, painting the whole wall corner-to-corner is the only true invisibility, and it is usually a 45-minute job.
Spackle is lightweight, fast-drying, low-shrink - built for small holes. Joint compound (mud) is for taping, skimming, and patches, dries slower but sands and feathers better over area. Small hole: spackle. Anything with a patch: compound.
Spackle: an hour or two for small holes. Joint compound: 24 hours per coat, fully dry before sanding. Rushing paint onto damp compound is the main cause of cracked, bubbled repairs.
Nail holes filled flush and touched up will pass most inspections. Use a fine-tip spackle pen or a tiny tub plus a card edge, and ask the landlord or agent for the wall paint name - many keep records, and a matching dab beats an obvious white spot.
Hairline corner and ceiling-line cracks get flexible caulk or fiberglass tape plus compound - plain filler alone re-cracks as the building moves seasonally. Wide, recurring, or stair-stepping cracks above doors can indicate settling worth a professional look before cosmetics.