I'd read years ago to use lye to rust / corrode bare metal. That's easy enough to get in oven cleaner. Spray and leave it on. Reapply. It'll start to pit and age in maybe a week or so if you don't rinse it off. I also spray it with salt water after the metal shows corrosion from the lye. On the wood finishes it'll strip the protective coating right off and keep destroying... uh hm, I mean aging it pretty quickly. Once the varnish is gone I spray it with water, soaking it and let it bake in the sun where the pores will open up. Turns it old real fast doing that.
Funny, out west here we have to come up with ways to do what wet / salt / snow country does naturally - lol.
Always enjoy your posts. Keep it up and Merry Christmas to you and yours as well.
Edit: Oh and I almost forgot, if it's thick enough metal, placing it in a relatively cold fire will age metal immediately. Like a fire made with boxes and paper and maybe a little wood. But too hot and it'll warp it.