Dodging: take a piece of wire, a straw, whatever. Maybe take a coin or something else round and tape that bitch on the end, you have just created a dodging wand. While the enlarger is on(printing) wave the wand in fast circular motions over the desired area, this will make the affected area lighter.
Burning: Take a piece of paper or cardboard and cut a hole in it. While the enlarger is on use the hole in the paper to project a beam of light on the desired area, this added light will darken the area.