What is the proper way to sand between coats of paint for the smoothest finish?

Sanding between coats is what separates a truly smooth professional finish from a paint job that looks acceptable from across the room but rough up close. The process is straightforward: let each coat dry fully, sand lightly with fine-grit paper to remove texture, dust, and imperfections, wipe clean, and apply the next coat.

The first thing to understand is grit selection. Between coats on walls, 220-grit sandpaper is the standard — fine enough that it smooths without cutting too aggressively into the previous coat. On trim, doors, and cabinets where you're after a glassy finish, some painters go even finer with 320-grit between coats. On the first coat over bare drywall or primer, you might use 180-grit to knock down any raised grain or texture before fine-sanding subsequent coats with 220. Avoid anything coarser than 150-grit between finish coats — you'll create scratches that show through.

The most important rule is patience: the coat must be fully dry before sanding. A coat that feels dry to the touch may still be soft underneath in New Brunswick's humid summer conditions. If you sand too soon, you'll get sticky, gummy residue on your sandpaper and the surface will look torn rather than smoothed. On trim and cabinets where the paint is thicker, wait a minimum of 24 hours, and 48 hours is better. For latex wall paint in normal interior conditions, the manufacturer's recommended recoat time is usually 4 hours, but sanding to a truly smooth surface is easier and more effective after a full overnight dry.

For walls, a sanding sponge or a pole sander with 220-grit paper works well. Sand with light, even pressure using circular or cross-hatching motions. You're not trying to remove the coat — just smooth it. You'll feel the surface go from slightly rough to glassy under your palm. For trim and doors, wrap sandpaper around a firm sanding block to keep pressure even; sanding with just your fingers can leave low spots at the edges of your fingertips. On curved profiles like round mouldings and spindles, a flexible sanding sponge conforms to the shape better than flat paper.

After sanding, cleaning the dust off is just as important as the sanding itself. Vacuum the surface first, then wipe with a slightly damp cloth or a tack cloth. Paint does not adhere well over sanding dust — it creates a barrier between the coat you're applying and the one underneath, which can cause adhesion failure over time. On trim being painted with an oil-based or alkyd-style paint (like Benjamin Moore Advance or Sherwin-Williams ProClassic), wiping with a lint-free cloth dampened with mineral spirits after the tack cloth gives an even cleaner surface.

In New Brunswick's humid summer months, dust generated by sanding can settle slowly in heavy, humid air. Working with a window cracked and a fan drawing air out of the room helps clear dust faster and gives you a cleaner surface to paint. For the absolute smoothest finish on cabinets or high-end trim work, this is where professional spray application — with proper surface prep between coats — makes results look factory-finished. A brush-and-roll approach can still look very good with careful sanding, but spray application minimizes brush marks to start, so there's less to sand between coats.

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