Media blasting and citric acid bath. Those are the fastest and most effective. I've built elaborate electrolysis cages. Still end up baby sitting the project for days making sure every single angle has line of site. It is just a miserable experience that produces terrible results unless one micro manages it. Where as I can blast everything in real time, and have a coating applied same day. Really intricate components with lots of interior access challenges is solved with citric acid at 32.2C. Many times I can have those components coated same day as well.