Fast ways to draw brush outlines on a DrawingArea

["Keith Feesh" <gummybassist gmail com>]

Hello, I have been developing a drawing application for quite some time now
and I have implemented an outline system
which shows where your next drawing operation will go (just load up the
gimp, go on the paintbrush tool and select a size 11
brush if you don't quite get what I mean).

The way that I do things now includes redrawing the entire canvas every time
the mouse is moved, in order to clear the old
outline's drawing, and then to redraw the outline once again. This brings my
system to it's knees and I figure there must be
a better method, just I can't think of any method. Any hints would be great.