Mortalis

Most any ficus other than Benjamina you should be able to defoliate when its starting into a growth period. That time depends on your location if your growing under lights, just in a window or placeing it outside ect... Ficus goes into "rest" periods where there is little growth then into bursts of strong growth.. do it when it just starts to grow after a rest.
To be on the safe side you can take all but a few leaves and get a similar effect to total defoliation.

On Benjamina leave 1/4 of the leaves unless its REALLY healthy.

I keep a very close eye on mine document every new leaf and you will get to know when your ficus enters its growth periods.