Interesting. I have heard of immersing the iron in a molasses bath, but this is a new one. A friend used the molasses method and it rounded off the edges around the fuse hole so that stuff must be caustic. Otherwise it worked fine.
I still have good results with electrolysis using baking powder. Just did an Archer bolt and a bunch of canister shot ahead of Mansfield, but usually I outsource most of it as its a messy mess and I don't always have the time for it.
James projectiles are the devil with their ribs and I have heard the zinc and lye method is better for them, but if I did get one, I'd just hand it over to Carl along with a few bucks and let him deal with it.