EXT's EV68 is the ultimate friction reducer for mountain bike forks!
Administered by either replacing F*x or RS original lowers lubrication or by adding a drop at a time from the top using the smaller 100ml bottle.
Even on a sticky fork in need of a service a few ccs of the EV68 past the dust seals will make it feel 'just serviced'. Typically makes enough difference to the sliding friction that we can add 4 clicks or so to customers rebound settings!
Looks expensive but is used just a few ccs at a time...