A mirror finish will not allow the ring to seat, tell him to use the same
de-glazing stones he uses on a regular ringed engine. It will most likely
be a 220 grit.

However, most mechanics that haven't spent any time in a 2-cycle engine
engine shop tend to use too fine a stone. They are used to working on four
stroke engines that have 3 sets of rings. In the single ring application, like
our engines the ring should seat immediately.

Shop him these pictures if you can. This was a rough cylinder. I de-glazed
it by hand with 180 paper. This is what it should look like. Trust me, I did this
Professionally for 20 years. These scratches eventually wear off, but in the
meantime, the facilitate ring seal, while at the same time permitting some
oil retention on the cylinder wall to keep the new ring cool and lubricated while
the new ring is seating.

Ask your friend if this makes sense to him.

FBD.