Use emory cloth or sandpaper to "dress" your bird bill. Most of the old men wouldn't got to the field unless this was done. smoothing up the surface of the bill will allow the twine to pass through as the bundle is kicked out. The bill doesn't open after it has grabbed the twine, it just pulls through to make the knot.
Tractor Supply carries a line of reprints by Lyons Books, one of which is called Farm Machinery, practicle hints for handy men. Was originally a textbook from the turn ofthe century, lots of old machinery operating info.