Streak-free walls are technique, not talent: keep a wet edge, load the roller properly, and respect that prep is half the job's hours. Here is the full sequence in painting order.
Riley Brand
Professionals spend as much time preparing as painting, and it shows in the result. Clear or center the furniture under plastic, fill holes with spackle and sand smooth, wipe the walls down (a sugar-soap or mild detergent wipe matters on kitchen and hallway walls - paint will not bond to grease), and run painter's tape along trim, sockets, and the ceiling line, pressed down hard with a card edge so paint cannot creep under.
Buy decent materials while you are at it: one good 'one-coat' quality paint and a $8 microfiber roller sleeve outperform two coats of bargain paint on a fuzzy $2 sleeve - cheap sleeves shed lint into the finish and hold too little paint, which is where streaking starts. Calculate quantity at roughly one litre per 12 square metres per coat, and assume two coats for any real color change.
Cutting in - brushing a 5-8cm band along edges the roller cannot reach - comes first, but only one wall at a time, not the whole room. The band must still be wet when the roller blends into it, or the doubled layer dries as a visible 'picture frame' around the wall. Cut in a wall, roll that wall, move on.
Use an angled 5cm (2-inch) sash brush, load the bottom third of the bristles, and draw a steady line a few millimetres from the tape, then push gently toward it. Two thinner cut-in passes beat one heavy one - heavy edge paint is what wrinkles and sags at the ceiling line.
Load the roller properly: roll it down the tray's slope several times until evenly coated with no drips - a half-loaded roller streaks, an overloaded one spatters. On the wall, paint a big W or M shape about a metre wide, then fill it in with vertical strokes without lifting the roller. The W distributes paint evenly before you smooth it; starting with vertical stripes from a fresh-loaded roller is what causes the heavy-light-heavy banding.
Work in metre-wide sections across the wall, always rolling back into the still-wet previous section - the 'wet edge'. Paint over half-dried paint and the overlap dries darker as a lap mark; that, and pressing harder as the roller empties (reload instead), cause nearly all visible streaking. Finish each section with feather-light top-to-bottom strokes in one direction and do an entire wall without a break.
Work top-down: ceiling (if doing it) first, then walls, then trim last - drips fall onto unpainted or to-be-painted surfaces instead of finished ones. Keep a damp cloth in your pocket for immediate drip patrol: a wet drip wipes away in one second; a dried one needs sanding. Check the wall with raking light (torch held at an angle) after each section to catch sags while fixable.
Recoat when the first coat is actually dry - typically 2 to 4 hours for water-based emulsion, longer in cold or humid rooms; the label time is a minimum, not a target. Rolling a second coat onto tacky paint lifts the first coat and makes a texture problem no third coat fixes. Between same-day coats, wrap rollers and brushes tightly in cling film instead of washing them.
Pull the tape when the final coat is dry to the touch but not cured - within about an hour of finishing - at a slow 45-degree angle back on itself. Fully cured paint can bridge onto the tape and peel off the wall in flakes; if you left it overnight, score along the tape edge with a utility knife first.
Wash water-based paint out of brushes and sleeves with warm soapy water until it runs clear, spin or squeeze dry, and store brushes in their cardboard keepers to hold shape. Decant leftover paint into a labeled jar (room name and date) for touch-ups - a sealed jar keeps far better than a quarter-full tin - and let unwanted paint dry out fully before disposal per local rules.
One coat almost always looks patchy - coverage evens out on the second. If patchiness survives two coats, the usual causes are un-primed filler spots ('flashing'), cheap paint stretched too thin, or pressing an empty roller. Spot-prime repairs and recoat.
On previously painted, sound walls in a similar color: no, two coats of quality paint suffice. Primer earns its keep over repairs and bare filler, on new plaster, over stains (use a stain-blocking primer), and for dramatic color changes - one tinted primer coat can save two finish coats.
Usually overworking: going back over paint that has started to set drags texture into it. Lay it on, smooth it once with light strokes, and leave it - emulsion self-levels better than people trust. Also check the sleeve nap: 10mm medium nap suits most walls; long nap adds orange-peel texture.
Best result: turn off the circuit and unscrew the faceplates rather than taping around them - cutting in behind a removed plate takes seconds and looks factory-finished. Never unscrew live accessories, and keep paint out of the socket itself.
