I went ahead and recorded a short walkthrough (it is silent because I don't have a mic, but I explain each step with text). These videos cover the 2 files that need to be edited to properly get the desired CF to show up in the Edit Player Screen in NBA 2K18 - the appearance_info.RDAT and hihead.SCNE file inside the png.iff archive. Hopefully this video helps. If it goes too quick, just pause it as needed.
As for what you place in your modded folder, you do not have to make any changes to the face.iff archive from NBA2K17. And for the png.iff, you will end up with 4 files in there:
1) The appearance_info.RDAT file that you made changes to
2) The hihead.SCNE file that you made changes to
3) ^The original .model file, only with the part of the file name that says "player" is changed to "hihead"
4) The original .mathnodes file
*Beyond these 4 files, the rest you can add in like you would in any 2K18 file (3D facial hair, hair, etc.). In my case that is shown, I did not need to add any of those since Reggie Miller does not have any 3D hair or facial hair.
appearance_info.RDAT
hihead.SCNE
What goes into your modded folder