I see pictures of some people hunting with only that little preconditioned area. I never subsribed to that. I condition the entire surface of all my pot calls. If you only use that little preconditioned area, you give up other areas of the call that may have a different tone. The tone of that call gets deeper from the edge towards the center. Additionally, if that's the only area you're using, you're having to give it some touch up conditioning more often. As far as oils go, that has never been a problem for me. I don't touch the surface if I can help it, and if I do my hands aren't oily. And I'm usually wearing my camo hunting gloves when I'm using it in the field. And it's pretty easy to see the direction of the abrasions so I can strike perpendicular to them.

[Linked Image from i.imgur.com]
https://vcdl.org/