If you want to use lube, don't use cooking oil. Get something proper like a sewing machine oil or WD40. Some people mentioned silicone based lubes previously.
Cooking oil is thicker and isn't as good as proper lube
That's just an image from google. Mine is something like this,
Its real cheap, made by some student/guy who does this as a side project. He hasn't been replying in my local forum though so I don't know what happened.
My friend has an Omega headphone stand just like that for his Beyer T90. It broke the plastic parts on the headband so he had to change the headband with his DT880's. So yeah, maybe HD650 has better stretch-tolerance, but just in case get stands that hold by the headband without stress. Something like this,
The S500 is not harsh at all. The highs are subdued compared to other cans. They're once of the smoothest cans I know. Harsh would be something like an AKG K550 or Sennheiser HD800 without proper amplification.