The Six series grip frames are part of the frame, not detachable like on the Ruger Single actions (Blackhawk, etc.) They are all steel, not aluminum. For the ultrasonic cleaner, a 50-50 mix of water and 409 will work if you don't want to get a commercial firearms cleaning solution (they aren't cheap but they do the best job).
I use one called MC Gun Cleaner from the Chautauqua Chemicals Company, Ashville, NY. You only need 1 part cleaner to 40 parts water. It's safe on steel, aluminum, and polymers, and it's biodegradeable. I've used it for years in my gunsmithing business and it cleans ALL the gunk out of firearms. (I have no stake in the company, I found them a long time ago and will always use it to clean guns).
If you use an ultrasonic, I have found that the parts will get hot enough in the tank that once you pull them out and give them a quick spray of air or wipe them down to remove the majority of the solution, they will dry themselves out. Then you can inspect them and reassemble using your favorite gun oil where needed.