I can tear through backs of napkin, but typing a diagram usually stalls me out, even though I'm pretty fast on a keyboard and the specifications seem pretty sim

I can tear through backs of napkin, but typing a diagram usually stalls me out, even though I'm pretty fast on a keyboard and the specifications seem pretty simple. Is it just my lack of practice, or is diagramming on a keyboard always awkward and slow? Or... do people generally surpass their freehand speed with enough practice, like with typing? If not, is the ideal solution here a digital pen or wacom tablet with diagram detection / normalization software? Scanned napkins to mechanical turk? Something else? Note: No disrespect though, the link is an amazing project for those that must type charts.