Working with layers is easy but you have to know your end result before you start mixing channels and curves to create great lighting effects. It's a fine line between artistic photography and great image manipulations and an over blown theatrical mess.
[Aperture Vs. Depth of Field] When you widen the aperture, the depth of field becomes shallower, and vice versa. That’s not all the Aperture does though, as it also affects the exposure. The DoF is also controlled by where you focus, and how far you are away from the subject.