I use 4B. Use a soft eraser. The gray clay-like 'kneaded' erasers suck up the black mark without abrasion damage to the paper. A mechanical 'clutch' pencil with large gauge lead lasts for years. You can sharpen often for the best point. Save trees and money with sharpenable lead.
Prepunched paper is much more expensive.
Patience and precision while punching will be rewarded with excellent registration. When inking with pen, clean pen at every stopping point with ammonia and a toothbrush. Dirty nibs are unreliable. Hone or replace the nib frequently. Fresh nibs are easier to control and produce the best quality line.