I may have asked this but forgotten, apologies if so.
A 12 inch blank file will only go half at a time in my furnace to soften, 'when' must I turn it around to soften the other half, in other words do I let it go cold?
It sounds to me that you need a portal in the back of the forge to let you stick the steel out the back. You then work the steel back and forth from the front heating the steel evenly.