I use a very fine powder
Richard Findley does a poured pewter cabochon for his box demos. Fun to watch, and a nice result, but a lot of work. When he demoed for our club, I had him do the cab in imitation ivory, and that worked well in our limited time slot.
I often use key filings for "brass", because I like the texture, as well as the color, but I also have a small bag of "atomized" brass powder (probably got it on Etsy) from "NorthernWestStuff". I prefer this to molten metal from a practical POV (!), but I have to say your pewter example is lovely. For dispensing the brass powder, I put it into an empty, small CA bottle with the long, fine tip. You can dump/squeeze out just a little at a time and get it exactly where you want it with no waste or contamination elsewhere. With a little Thin CA it makes a great fill, and it sands out to look "almost" like solid metal. If you look really closely, you can see a slight granularity, but, from a distance, it appears solid. I like the brass color on cherry, but f you want a "silver" color, like pewter, I'm guessing you could probably also get atomized aluminum. Here is an example of a small brass powder fill in punky cherry.
