It is amazing how much dirt can cover the surface of the keyboard and mouse just over few months.
Luckily I don't eat or drink while working with the PC, otherwise all kind of bits and pieces would fall in between the keys.
When I couldn't see the characters clearly anymore, with the PC shutdown, I took a sheet of tissue, soaked it with spirit from a bottle that I keep for the thermometer and went over the keys one by one, changing the tissue from time to time and followed the warnings on the bottle on how to use the fluid.
Using a cotton swab would be better, so as not to touch the fluid with fingers.
After just few minutes I got a brand new keyboard and mouse, all bright and shiny.
It is possible to take out almost all the small keys using a screwdriver, but be careful to notice their exact position so as to put them back again the way they should be, preferably take them one by one.
It is not a pretty sight what lies underneath the keys.
This might be a good idea for a young lad to make few quids doing the rounds at other people's houses and offering to clean their keyboards and mice. Beats a car wash anyway.