Always stir from the bottom up as this ensures the mixing of the clearer layer of thinner at the top with the heavier, pigment-laden material that settle at the bottom. For a more uniform colour among multiple cans of paint, boxing (below) is recommended, but not usually necessary.
Different cans of paint, even in the same colour, may have some slight variation in them. Use a system called “boxing” that will assure that there is no mismatch among the cans of paints. This is done by mixing all your paint into one large container until the paint’s colour and consistency is uniform. Make sure that you gauge how much paint you need as running out and trying to match the colours again may be difficult. You can also work from one can and whenever it gets down to about half empty, refill it with paint from one of the other cans and stir thoroughly.
Straining and Thinning
If you encountered blotchiness on oil-based paints, strain it through a nylon stocking to separate them. When thinning paint, make sure you do it slowly so as to not over-thin it. Add water (if latex) or thinner (if alkyd) as necessary.
For a professional-looking paint job, the paint must be spread evenly onto the surfaces without running, dripping, or lapping onto other areas.
Dip the brush to about one-third of the bristle length and tap the bristles against the side of the can to remove excess paint. Dipping the brush deeper will overload the brush. If you load up too much paint, it will run on the surface and drip onto woodwork and floors. If you apply too little, you will leave lap marks and bare spots resulting in incomplete coverage. Dragging the brush against the lip of the can causes the bristles to wear excessively.
Cut in the edges using the narrow edge of brush, pressing just hard enough to flex the bristles. Keep an eye on the paint edge, and paint with long, slow strokes. Always paint from dry area back into the wet paint to avoid lap marks. Brush wall corners using the wide edge of the brush. Paint all open areas and cut in before the paint dries to avoid lap marks.
To paint large areas with a brush apply paint with 2 or 3 diagonal strokes. Hold the brush at about a 45 degree angle to the work surface, pressing just enough to flex bristles. Distribute the paint evenly with horizontal strokes. Smooth off the surface by drawing the brush vertically from top to bottom of the painted area. Use light strokes and lift the brush from the surface at the end of each stroke. This method is best for oil-based paints, which dry slowly.
When using a roller, run the roller over the ridges in the tray to eliminate excess paint (the roller cover should be saturated but not dripping), then paint strokes with the roller down and up in repeated overlapping “W” pattern. Cover the entire surface, then paint with non-diagonal strokes, all in one direction (top to bottom on walls; any directions on ceilings).
Ceiling Painting Tips
Paint the shortest side of the ceiling first or from the end that receives the most light, as this will make it easier for you to see if the whole ceiling is painted. Unpainted spots (called “holidays”) will show up as dull spots in the glossy paint.
Start by painting where the light is best. This would be the ceiling, moulding on the “light wall”, which is the wall that receives the most light. Unpainted spots will show up against the direction of light.
Work in small areas of about 2 meters, as you want to be able to covered and finish areas before the paint totally dries up. Painting on large surface areas will involve a delay in returning to the next zone. Using the roller on dry paint surfaces would risk tearing of the half dried paint, giving rise to a blotched appearance.