MKV Meteor, it was a simple enough task

[Dornfelderliebe]

No, I make honing plugs that fit on M10 all thread rod, and use a cordless drill.
I run the honing plug with emery paste to remove high spots, and try to run it up and down while spinning.
Then I finish off with fine wet&dry on a piece of wood dowel turned to a close fit in the tube.

Your piston idea will probably no be consistent enough in diameter to accomplish what you want,
I have more belief in the close fitting wood dowel with wet&dry paper.

Nice one Evert. Not having any engineering facilities or suitably sized wood. I searched for another 25mm tube. Low and behold I found 25mm plastic conduit in the screwfix catalogue, wondering whether plastic is strong enough I tried it.
I glued a section of 400 grade wet & dry to it and gently had a go. I usually use different tubing with a slit to secure wet & dry wrapped around to polish cylinders so I was not worried about doing this carefully.
Whilst rotating it, I could feel alternating resistance then free movement. When moving forwards/backwards with a few degrees movement each time. I felt no difference.
Sadly my glue is not waterproof and after 5 minutes each on the two Mk3 cylinders I am working on, the paper came loose.
This may point to the uneven profile. I currently waiting for the glue to dry for a second attempt.