First off, the process will work with low draw. If you want to increase the draw, you can add more soda or a 1/4 - 1/2 cup of phosphoric acid ("metal prep" in most home centers or hardware stores--In the paint department). Also, don't use copper wire in the solution. Use steel wire or old coat hangers.
The process converts the iron oxide (rust red) into a ferrous compound (black) that must then be washed off. When using soda alone, the process will stop when the rust is converted and no metal will be lost. If you add the acid, you could loose metal over time but it does help the flash rust problem.
It will take at least over night to do most parts. I've left parts in the tank for three days for heavy rust. It is a slow process so don't rush it.
Here's a piece I did some time ago. Before:
After (With a little paint)
