Wow, there sure is a lot of techniques on this thread for glossy (thanks Colleen) but here is one I didn't see mentioned and it's one of my favorites.
Stamp and emboss your image, then use the aqua pen and watercolor crayons to brush on the color. It leaves a very nice watercolor effect. You just place your bursh onto the crayon to pick up color. If the color doesn't pick up right away on a new set just keep at it or scrap off the tip a little. A little wax coating might be covering the new ones.
The crayons can be purchased at most stamp stores and there is more than one brand name. My sister in law found mine at a convention.
They last a long time, the tip of mine still isn't gone and I've used them for over two years.
I did purchase some at one of the local craft stoes for about three dollars and they do not work. A good set should cost eight dollars or more depending on the store and the amount of crayons in the set.