I find that when I draw my characters for their first frame of animation -- or anything for that matter, not just characters -- I tend to zoom in a lot to fill in details and get a closer look at what I'm drawing. But doing this causes my graphics to each have lines with different a different thickness. One character will have thick lines, another character will have really thin lines.
Just now the only solution I can come up with is to drag another graphic on to the stage to compare the brush size to. Is there no way to lock the brush to one size, even if I zoom in?