After much messing about trying to use an old Bowden cable through as a guide / puller and it repeatedly becoming detached at the critical moment - very tight fit - I abandoned all that, reverted to just dropping the wire itself down after feeding a loop of stiff fishing line in through the lower hole, and pulled the loop out + wire when the dynamo wire had dropped through the loop.
I do think describing a fork with a hole near the bottom of one leg as “dynamo cable ready” is being not entirely truthful.