[George Formby]

Mmm.. I have read accounts on how pilots used to sync their propeller to their leader visualy by watching his prop. One in particular after an rpm guage went in/op, the pilot simply watched his boss's propeller..

S~
You are both spot on, the pilot would look thru his prop spin, line it up with the lead plane, that way both are visible, but to actually see the prop by itself is hard to do, unless the sun or some kinda anomaly.