Glazing is painting over an area that has already been painted and allowed to dry in order to darken the value or raise or lower the temperature.
The consistency needs to be a little on the thin side to allow the color underneath to show through. Also use a brush large enough to allow the least amount of strokes on the given area. Do not over work or lots of brush strokes will appear.
Of the primary colors Red and Yellow are warm and Blue is cool. If Blue is part of a mixture a dominance of it will make a cool mixture. (Cool green or cool purple for example).
If a certain area like a bright corner of your painting is too warm and is attracting too much attention you can "kill" it back by glazing with a pale blue. Glaze once with a minimum of overlapping and allow to dry. If this is not cool enough, repeat.
If a section of your background is a bit bland you can perk it up with a glaze of warm (Yellow or Red). Once you've improved an area in this way you will begin to see other opportunities.
When painting early on, watercolor dries 30% lighter in value, if this happens, glaze with the same pigment or mixture as the first wash. The result will be darker. Repeat if necessary.
I hope this helps with the glazing technique. Be sure to practice on test sheets to perfect this technique.
