I don't have a lot of information to add, but I wanted to list two
retail offerings to give Scott a chance to make fun of me.

Christopher Schwarz (former? galoot) says the PINEEZ makes a good
split nut driver.  Haven't tried it.  http://www.rosstools.com/

Our own Bad Axe recently started offering a variety of saw nuts:
http://www.badaxetoolworks.com/bad-axe-fasteners.html

In The Mighty Wenzloff's saw kit, he gives instructions on how to make
a split nut driver from a spade bit:
http://www.wenzloffandsons.com/saws/kits/Handsaw_kit_instructions2.pdf

Mark
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