I would totally disassemble the keys. Take the caps off, disassemble the switches, and toss the slider, the spring, the tactile leaf, and the key cap in a bowl of hot water with a few denture cleaning tabs.
It takes quite a while, and you should pay attention to the orientation of the sliders. I'm told it makes a difference, but I haven't noticed one on my dell. Make sure you let everything dry COMPLETELY before reassembling. Also, be careful with the leaves, as they have a tendency to stick together when they are wet.
Be patient, pay attention, and make sure you have a strong, but small, magnet handy when you're reassembling, and it should not be too much trouble.
It was the first mechanical keyboard I took apart to clean, and it was pretty easy. If you have questions, the wiki has instructions on how to disassemble and reassemble the switches.