FYI, I recently had a good experience with the services of Sergy Laylko at
rustbluing@yahoo.com. Sergey was very nice to deal with and turnaround was 3 weeks. Work was as good as any I have seen. He is not a Luger specialist but is capable of doing any finish you require.
Pictures attached of my shooting broomhandle, rebarrelled for 9mm and extensively restored/rebuilt. I painted the milled out sections with teflon/moly oven cure finish to hide some minor rust pitting - didn't want to remove any more metal in the interest of strength. Sights were zeroed at Bolsa Gunsmithing, came out pretty good if a little expensive for a shooter.