My unscientific rule of thumb from lots of trial and error is:
a) if the switch housing is matte, like a milky or black, use a grease like Krytox 205
b) if the switch housing is glossy or smooth (like a clear housing) use an oil like Krytox 105 or 106
c) if it’s a Kailh linear box switch go with a grease regardless of the switch housing material
Also I tend to put a very light dab of Krytox grease on the spring on each end because there’s no chance of it migrating like oil might.
