The process can be a little time consuming, but is quite simple. They'll take the sections of hair to be highlighted and underlay them, one at a time, with aluminum foil. Then they basically use a special paintbrush and apply the hair dye, wrap the hair section in the foil and let it set. You might sit under a dryer for a while, and then they'll wash out the excess. A good quality dye from a salon can last a long time without fading, and never quite fades away.