There is a pad maintenance post but ill put it here too:
i want to add and ask about a few things mentioned here:
For leathers: I would not use most products that are made for boots, shoes, jackets. Most of the stuff has a synthetic or petroleum base which i would not want sitting on my skin or any nice leather. I have high end Saphir stuff and i still wouldnt use it on the pads. Mink oil and neats foot based products tend to clog pores, making it heavier and much less breathable. Once again good for waterproofing boots but not earpads.
My vote would be Lanolin. Its cheap, doesnt rub off and can be found easy as its medically used to help sooth breast feeding. I use it for everything leather i want soft, light and breathable.
The audeze stuff is the closest, some moisturizers, lanolin, and beeswax to protect. Over saturation does more harm than good and im sure doesnt help the foam underneath. Just make sure its clean before application.
Velour: this is my kryptonite. I shower and wash my hair before usage but this stuff soaks up all my skin oils and it kind of gunks up and melds the pads surface. When i wash these they never seem to come back nearly as soft or fully clean, and is normally a death sentence for the foam. I will take any suggestions on how to keep these clean as they usually gunk before the foam deteriorates. I even find if i out them down on a piece of paper they will rerelease the oils it absorbed onto the paper. In oily but i dont think im that grungy
Suedes: they make erasers and brushes but those are more for longer naps and more rugged applications. I have a pair of audeze vegan pads that are sooooo soft but am afraid to use since they may get dirty like the velour and i cant clean them