My PPK/S, manual lists a brass punch for rear sight adjustment.

I know I thought the same thing, went to the Walther forum, (I know, I know,

) But a knowledgeable member suggested, wrapping the brass punch in electrical tape, just a couple of layers, and a hand towel. Than with a urethane or rubber mallot, start off easy, and give the sight some "love".
Mine was perfectly off a "hair", and with a shorty short barrel, put all my groups perfectly to the right of the x-ring at 7 yards.
So, I tried it and it did work, without marring or marking the sight at all.
They do make tools for this type of thing,...but it seems like quite an expense, for the frequency of use. Hopefully not often!
Just thought I'd Pass it along, I didn't like the idea of "smacking" my pistol either, but it did work without marks.
Good Luck.