I don’t go crazy on my iron finds, this is my process: First, I use a mini hatchet I have- you can use mini hammer instead, and I bang off what rust buildup I can. Pliers can crunch off the buildup from iron rings and square nails/spikes. Second, I use either wire wheel on bench grinder or coarse wire brush.
Two ways to finish: 1, boil paraffin a wok and throw parts in for few minutes or 2, brush on matte modge podge and let dry - both work well to preserve the iron items but the modge podge is faster and easier.