I've successfully removed excess lanolin with hot water, but you have to be careful not to agitate it too much or it will felt and shrink. I think it helps if you have some non-lanolized wool to add to the water to soak up some of the excess so it doesn't redeposit onto the original cover. I would put a couple inches of hot water and a few drops of baby shampoo (not wool wash) into a dish tub and add the overlanolized cover to that. Squish it around to help release the extra lanolin into the water, then add more water to cool temp slighlty, then add the new wool to soak some of the lanolin up. You can also pour near-boiling water over the greasy cover in the sink but don't squish the wool around, just let the water drain through.