Like Byron, I tend to use the stencils for this sort of thing. I fill the selection on a separate layer using the Fill Tool or painting it in with another tool and then turn it into a stencil. When it's not needed, I just hide the stencil (via shortcut key or stencil panel).
You could also fill the selection on a layer on top of all the other layers you're working on. This can act as a mask while you work on the layers beneath it. When you've completed the rest of the layers, select the top layer (the layer which you filled your selection in on) by going to Edit > Select Layer Contents to select the painted area and then delete the top layer and merge the rest. Now hold Ctrl and hit "X" to cut away the area that is selected, leaving the empty border.
Nothing is easy to the unwilling.