To get a good diy paint result you have to start with a good surface. This means filling cracks, cleaning off stains and most importantly, rubbing down to get a smooth surface. A good supply of sandpaper is the most important tool in getting a good finish. The quality of paint is pretty much secondary to the quality of the surface you paint on.
Don’t underestimate the importance of that one piece of advice. In order to do it properly, you have to spend time preparing the surface. Use a sander (or sandpaper wrapped round a block of cork) and rub every inch of the wall. It is boring, tiring work, but the results really do speak for themselves.
Next, wipe off all the dust with a damp cloth. In all aspects of painting and decorating it pays to be clean.
Use masking tape and old newspaper to mask off edges, light switches and anything you dont want to get paint on.
Painting with a brush or roller?
I suggest you apply the paint using a brush. Pint rollers give a mottled finish while a well brushed wall will look smooth and professional. A four inch paintbrush is fine for an interior wall.
If you don’t mind the slightly bumpy wall finish that a roller gives, then go ahead. Painting with a roller is undoubtedly a lot quicker.
Start around eye-level, painting horizontally and then vertically. Finish with an almost dry brush in short gentle flicks, to ‘lay-off’ an even finish.