Here you go. Water and a fresh batch of natural small aquarium gravel. Nothing else in the tumbler. The gravel is about 1/2 the volume and just enough water to be level with the gravel. I checked it about every 30 minutes and it didn't take long but about three cycles.
Not surprisingly, if you use the same gravel for a long time it wears down and isn't as good at getting into the finer details. A fresh batch can make a huge different in time/detail. By "natural" gravel, I mean the kind that has all sorts of shapes and sizes and natural colors, some of which is pretty small and/or sharp. The gravel that's more uniform and all shaped like little boulders isn't going to get into the details. I've thought about making a mix that includes crushed seashells. You have to drain it in a finer sieve to avoid them going down the sink.
The shiny highlights aren't so harsh in person. Mine looked about the same or worse than the one in this thread. None of the grooves or finer details could be seen even after using water and a toothbrush.
I have some civil war era buttons that lack detail due to the patina. I have no plans to tumble those.