2mm one of these works pretty well. Doesn't have the wood bit so doesn't make as much of a mess: http://www.rotring.com/en/mechanical-pencils/265-rapid-pro-mec

2mm one of these works pretty well. Doesn't have the wood bit so doesn't make as much of a mess: http://www.rotring.com/en/mechanical-pencils/265-rapid-pro-mechanical-pencil-3501170949351.html http://www.rotring.com/en/mechanical-pencils/265-rapid-pro-m... I use a 0.5mm one for everything.