I have a set of very, very small dinging hammers that I got a few years ago. They range from about 3/8 in diameter with 1/2" faces and 1" long to 2" long with 1" faces. Long skinny flexible handles. I've got photos somewhere. They were made by a guy in Ca some years back and no longer available.
Cass Nawrocki has some similar.
These are used to move aluminum around. Lots of fast light blows in the right space, usually with no backing dolly. Metal moves but no marks. I've used them on Monique with good results.
I expect the magnesium hammers work about the same. I saw one once at a swap meet but didn't know what it was and didn't buy it.