The willow leaf ficus is tough. You can actually do this much work to it all at once, and it will bounce back just fine. However, it needs a lot of sun, warmth, and humidity to bounce back nicely. It would have been better if you did this in the summer when you can put the tree outside in full sun. Next time you hard prune and defoliate the whole tree like this, wait for the summer.
Even a metal halide lamp doesn't work as well as the real sun. Artificial light or sun light through a window (even the south facing one) won't penetrate the lower branches well enough for it to budback everywhere. So instead of getting 4 shoots coming out of one of those stumps, you'll just get 1 or 2. This will actually set you back on ramification.
Since it's already done, I would put it on a south facing window sill and spray water on it several times a day. Spidermites LOOOOVE willow leaf ficus. Spraying water on it will keep them at bay while at the same time provide good humidity for it. You can also add more humidity by putting the pot on a big tray full of pebbles and water.