1) The plant should be a mature plant. No way an immature dendrobium can flower no matter how to treat it ~
2) The plant should be strong enough to flower. Weak plant with thin pseudobulbs can never flower .
3) Main triggering factor is low temperature. You cannot have massive bloom if temperature does not go low enough no matter how dry you keep the plant. winter OUTDOOR temperature in most of the place in HK can trigger flower buds formation.
4) When all psedobulbs stop growing and stop becoming swollen (ususally in fall), allow the plants to dry several days more after all potting medium is dried out completely. Water thoroughly afterward. Don't let any pseudobulbs dry and shrink all long the winter and spring.
5) give the plant plenty of sunlight during winter time. Dendrobium can receive as much as direct sunlight in winter time.