Since it always takes me several attempts to find lines, I have a lot of rubbed-out debris around my drawings, which is picked up quite visibly by the scanner.

Since erasing these smudges and creases manually with the brush tool is a bit of a pain, I'm wondering if you guys know a better way? I found that a High-Pass filter picked up exactly the lines I wanted, but of course this came out as dark grey lines on a grey canvas. I couldn't find a good, clean way of turning this back into black/graphite lines on a white canvas.

So, your opinions on how I should do it? I can post pictures of the scan in question if this is a situation-based thing.