Odd bits of paint left over at the end of a job are often kept in the original can in the vain hope that one day it will come in useful for touching up. Most of the time, when you take the lid off these leftovers, the paint has set hard because the seal on the lid no longer fits tightly. Left-over solvent-based paints will leach out fumes from ill-fitting lids and can be a serious fire hazard. Any left-over paint is better stored in a glass screw-top jar of the right size. Label the jar with the make, type (emulsion or gloss) and colour. This way it will keep for years. If the manufacturer has ceased making the same colour, you will be able to have it copied using the colour-mixing systems now available in paint and DIY stores. In the short term, to stop a skin of paint forming on the top, a circle of kitchen foil, cut to the approximate diameter and placed on top of the paint before the lid is replaced, will solve this particular problem.
Using a Paint Kettle
You'll never see a professional painter and decorator dipping his brush directly into a can of paint. Instead a small amount of paint is poured from the tin into a kettle so that the rest remains completely clean and uncontaminated by grit and dust.
To avoid cleaning the kettle each time a new paint is used, professionals will line their kettles with kitchen foil. When one paint is finished with, the foil is removed and thrown away, and the kettle re-lined for the next paint.
Clean brushes and rollers by washing them thoroughly in warm water. Once again, it can be useful to condition brushes before storage.