do you mean like the ones i used to do? well, there's two different ways.. you can make it a brush or you can mess with opacity, but i prefer the brush way. in order to do that, you need to take out your rectangular marquee tool, and select the area you want to blend in. go to edit>define brush, and name it. then, take out your brush tool, set the blending mode to multiply, and take out your brush (of the pic) and brush where you want it. ^^,