KRYTOX GPL 205G0 Switch Lubricant
The Krytox 205G0 grease lubricant is the perfect consistency and base oil viscosity for keyboard enthusiasts. It's made for Topre and linear switches but will function superbly with any tactile switch of your choosing.
Thanks to its indefinite shelf life you won't have to worry about purchasing another one for a long time, or it degrading your keyboard and compromising it.
It comes in a handy 5ml vial which is enough keyboard lubricant for around 500 switches.
Do take note that you'll also need a small paintbrush to apply the keyboard switch lube.
Other handy accessories include: a switch station, a switch puller, and a switch opener designed for your brand of keys.