Prep, prep, prep! It's so important to do this first. Select your paint, but how much to get? To calculate this you need to do some measurements. Add together the width of all the walls and then multiply this number by the height of the room, from floor to ceiling. The result is the room's square footage. Because you will probably use a different paint on the doors and windows, subtract those areas from the room total - just take off around 2 square metres for each door and around 1.5 square metres for each average-sized window in the room. You end up with a number that is close to the actual wall area you will be painting.

A general rule of thumb - 1 litre of paint will cover between 6 and 6.5 square metres of wall. So, to calculate how many litres of paint you will need, divide the total paintable surface area by 6.5.

Remember that drywall will absorb more paint, which means you’ll need to buy slightly more paint, even if you’ve coated it with a primer. Are you painting in a light or dark colour? If you’re using a dark colour, you will probably require a tinted primer, or allow for two coats of paint. Don’t forget about future retouches. Always round the required amount of paint up, because you can use that paint in the future to touch up and remove stains and areas of wear and tear.

Golden rule

A golden rule for painting is to start from the top and work down, so ceilings first. If you are going to be painting the walls differently from the ceiling, you can run a line of masking tape along the width of the wall up close to the ceiling, which will give you a clean line between the two colours or paint types you have chosen.

But before you even pick up a brush or a roller, you may need to lightly scrape off any old flaking paint first with a blade, and use filler in any cracks – and because there is always some slight movement in Portugal, hairline cracks are quite common and easy, but bigger cracks will need careful filling and smoothing off with sandpaper before painting starts.

A roller is easy to use and will cover a large area quickly, but start the edges first with a brush, ‘cutting in’ up close to a line of masking tape on the ceiling now, and the corners where two walls meet.

Then switch to a roller - for flat walls use a smooth roller, for textured walls use one with a rough nap cover.

Dampen the roller before you start with a wet rag, as this will help the roller to absorb paint. Resist the urge to plunge the roller deep into the paint! Just touch the roller to the paint in a paint tray and roll it a little to get enough on the roller so it doesn’t drip. Starting at the edge, start rolling in a zig-zag fashion, but not too fast or you will get paint splatter everywhere, and turn the roller sideways to get close to the ceiling and baseboard or floor. If you run out of time and can’t finish it all in one session, putting the lid back on the paint can stop a ‘skin’ forming, and a handy tip is to wrap the roller in plastic film, then a plastic bag, and place it in the fridge, and it will be ready to go the following day.

Once the walls are dry you can start on the baseboard or window frames - again, using masking tape on your newly painted walls will be worth the effort when you get a clean sharp edge where the two different paints meet.

Lastly, clean up. Follow the instructions on the paint tin, and ensure all paint is removed before air-drying both brushes and rollers. Now sit back and enjoy your room’s new look!