So I finished the darkening the hilt and I'm happy with the result. Not 100% perfect, but it gives the effect I'm hoping for. In person, it looks a lot more like weathered steel than weathered aluminum now. The "brightness" of the metal is gone.
The diluted Aluminum Black method worked really well. I put them in a big bin full of water with just a little bit of Aluminum Black. I was able to watch the hilt slowly change darker and darker until I felt it was just right. It felt like I was BBQing a steak or something, watching it slowly cook. Afterwards, I sanded for awhile with a very light touch and very fine steel wool. I was looking to clean up the aluminum while keeping the effect uniform.
Unfortunately, I didn't take many pictures while I was in the process, but I have a before and after pic.
This was my Ben Solo hilt from Phoenix Props. Here are the two main pieces of the hilt after I cleaned them up for the Aluminum Dark bath.
And here is the finished hilt in my cabinet.
Thanks to everyone who provided advice on this. The hilt was driving me a bit crazy so I'm glad it's complete.