Just starting to reloading for my 300 and so got some information on Youtube about cleaning cases with an Ultrasonic cleaner and some home made cleaning fluid (distilled water, vinegar, salt and dish soap).

Main advantage seems to be the ability to clean inside the cases, I'm really happy with the results, I will clean again after decapping to get crud out of the primer hole, but this preliminary cleaning means a clean case as it goes into the decapper/resizer

I do a quick tumble, then size/decap.

Then run them in US cleaner. They come out sparkling clean.

I was also told to run them through a baking soda and water mixture to neutralize the vinegar.