flash with m6
...here's my reallllly late response.
back in the good old days -shooting fashion- i used to use a wee tiny peanut of a flash to trip the slave unit on my main flash & umbrella rig. at the distances i was working it added negligible amount of additional fill and freed me from being tied to a **!%***@+!!!! sync cord. on my budget it worked great.
i did have to overcome something of a "flinch reaction" to seeing the flash in the viewfinder. with an slr - except for a either my canon pellix or the (then) newer EOS RT - i never saw the flash as a result of the mirror swing during exposure. funny i never noticed that effect with my oly xa...hmmm.
enjoy the flash and experiment...using mainly cameras with leaf shutters when i do use flash now i miss the effects of leaving the shutter open (lower shutter speeds) and all the neat ambient light you can pick up with a focal plane shutter.
NEVER FORGET BESLAN