After a few iterations, here was my design for a manual one handed solder feeding assistive device.  A 3d printed hollow tube forms the base and with a wire ferrule connection at the end for a metal blunt tip near the soldering iron.  The body has a cut away area to expose the solder allowing it to be pushed forward by just the thumb and two contours to all holding it like a pencil.  Original design used a leur-lock syringe tip but solder would snag up.  The wire ferrule terminal needs to be super glued into place but provides snag free feeding.

Solder spool sits in a regular benchtop holder.  More solder can be pulled from the spool by holding solder secure in the tube with thumb while pulling the whole contraption to get more slack.  Rounded funnel design prevents kinks in the solder from causing snags while feeding.