There is no need to provide darkness while it is still in bloom. Most flowering Kalanchoes sold today are hybrids and often do not require the complete night-time darkness recommended in the past. I'm not sure it is worth the bother. Usually keeping it on a windowsill in a room that gets minimal artificial light after sunset is sufficient to set new buds. Keeping it very potbound and allowing it to dry out more in winter also enhance flowering.
