Bolt jeweling is not rocket science, merely marking metal in a uniform design.
Years ago I jeweled a few bolts just for my own enjoyment and now wish I had saved some of the guns I did...but didn't...
The first one I tried without an "indexable" jig... unsatisfactory results & ended up doing it over again. For the next ones I built an indexer, I used an old typewriter from a thrift store. I removed the main body and just used the carriage parts, worked perfect, it would index very precise movements, both radially and longitudinally. The pattern could be a very fine spacing with only one notch of movement or widened by multiple notch's.
The indexer was mounted on a very plain drill press that was used to turn the cutting tool. The type of tool and amount of drill press quill pressure could also be used to change the pattern shape/size. Even 1/2 swirl patters are a possibility by moving the indexer on the press table so the quill drops the tool to the 10 o'clock or 2 o'clock part of the bolt, only engaging 1/2 the cutter. With this cheap indexer & plain press, I found that dozens of pattern variations are possible.
The cutting tools I liked best have already been mentioned...the small stainless steel Dremmel tool brushes (again, quill pressure will flare the brush hairs out to increase size or regulate amount of center/outer edge cutting). The second best I found (although you go thru a lot of them if using much pressure) is the pencil with eraser on the end and dipped in valve grinding compound.
The secret to pleasing work is equal movements and pressures with every cut...no exceptions.