I needed a primer pocket cleaner, as it was missing from the reloader kit I bought last week.
My solution, first 4mm but later sourced some 5mm stainless steel cable. Epoxied into a rimfire case makes one nifty wire brush for rapidly cleaning primer pockets. The 5mm suits large rifle primer perfectly.
Few tips if you want to make one... Cutting off a length to suit a rimfire doesn't have enough twist to hold itself together, so glue it in first before cutting next to case (solder might work too).
First I used a tiny dremel grinding disc, next time a super thin 4" grinder cutoff disc (~2mm for sheet steel and stainless). The grinder ran a little hotter so touch,stop,touch, stop kept the heat down.
If getting a cable sample from Bunnings, perhaps you could wrap it with electrical tape before cutting off 30mm using their cable/chain cutter. A nice neat square cut without creating frayed ends is the goal, then it cleans the corners of the primer pocket.
A very fine toothed hacksaw might work well for cutting off too, perhaps holding the cable in a second rimfire and cutting through that case.