When working on gesture practice, I now use an ink pen. Currently a "Faber-Castell Broadpen 1554 0.8 mm", but I'm sure it'll dry up soon, and I'll be out looking for something similar in the shops here.
I gave up using pencils for these quick gestures, as I caught myself making too many lines and not commiting myself enough to my lines.
If I draw a line now, and it is "wrong", I just leave it. It is part of the process to see the obvious mistakes I made during the sketch. I'm not looking for publishable results, I'm on a very shallow but permanent learning curve. Reflecting on my mistakes is just as important as drawing gestures on a regular basis.
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