[...] traditionally in pixel programs, once you pick a brush you can do everything as you would with a normal "pen-point". This would be ideal, but if it is much more complicated, then you can just make a different behaviour using similar code to current selections.
Here is the process of using a brush"
-You click the brush tool icon.
-You draw a rectangle on the screen.
-The moment you let go of the mouse, the brush is picked and you are moving it with your mouse. The bg color is transparent. If you started to pick the brush with right mouse button, then the brush will be cut from the image, and the rectangle is filled with bg color (or transparent color, if it is on a layer)
-Now you can click anywhere to paste the brush, or you can draw with it, etc.
It replaces the following steps:
-click selection button
-press ctrl-c [copy](or ctrl-x[cut])
-press ctrl-v [paste]
-press ctr-d [deselect]
So it is not as flexible as selections, but is much quicker to use for everyday manipulation.