Leather pants and olive oil are pretty good in the warm weather, very hard to get a grip and keeps away mosquitoes too.
You people into Olive Oil and Tea will want to check out Divine Tastes blog.
And there are some more masters techniques at Turkish Wrestling .
Yagli Gures is a traditional form of wrestling from Turkey. Obviously you can see why I'm a traditionalist from the pictures. Actually, the Ancient Greeks didn't bother with the leather pants, they just wore the olive oil. One of my local informants told me that, "The way to get a Russian woman is to wear lots of leather." I think I'm starting to understanding.
Oil as a commodity was not big in China until sesame oil and trees were brought from Persia during the Tang Dynasty (~600-900CE), so I doubt that oil was used in fighting there.
Matched fighting may be natural, but religions have spent a lot of time trying to regulate it. Wrestling would obviously be more entertaining if it was truly "no holds barred!"