G'Day Fella's,

GG 375, the first thing you need to do is have the action Bead Blasted to remove all the old Blued Finish. Then, in my experience if you want to have a highly polished Brno ZKK series action, the best bet is to use progressively finer grades of Emery Paper and then Wet and Dry, stapled to a piece of MDF/Custom Wood and "Draw File" the action with this.
Start with say 320grade and go to finer grades from there.

If you have NO "Hand Eye Co-ordination", pay a Gunsmith to do it!!!

The primary intention here is to remove only the top or outer crust of the Matte, Factory Sand Blasted metal finish that will be visible above the stock line, until new shinny metal comes through!
Your objective is not to remove lots of metal!!!
You should stop and retain the lettering and serial number on the receiver ring, which will still be Sand Blasted and the contrast between it and the high polished finish should look good.

I assume the reason that Brno sand blast their actions was to obtain a better Blued Finish on these Investment Cast, steel actions?
Look at a Blued Ruger action in natural day light and you will see what I mean!

Hope this helps!

HooRoo
From
Hommer