Even if I was just using a wood stick.
I'd have decarboned the cylinder before grinding in it.
Little flecks of grinding swarf and any sandpaper grit will be in the carbon now.
Wiping or rinsing wont get all of it out.
Ever wonder why we sometimes see top ends go scratchy for "no apparent reason" after a "port job"?
Ask the person IF they skipped the decarboning.
Gotta clean the combustion chamber.
Decompression valve or the hole plug needs to be removed too, before, doing any port work.
Spark plug too, unless you're using it to hold the cylinder.
Then the plug gets removed and tossed before final clean up.