Congrats on buying a "classic" handgun. I have an Interarms PPK/s, and I love it. I just got a new OWB leather holster from a local leathersmith for it earlier today, so now I can cc it from time to time.
There doesn't seem to be anything special about its design that would need some sort of special consideration when it comes to lube, so I would say lube it like you would do any other automatic. I use Tetra spray on the innards, and Tetra grease on the rails. Mine functions perfectly with all FMJ's I've ever fed it, and also with it's carry load of Cor-Bon.
If you can't find a leather pocket holster to your liking, let me know and I'll contact my local holster guy and see if that is something he would be interested in making. He will do semi-custom designs for me on occasion.