As always, it is useful to prepare our model with polygroups before we start to sculpt.
When working on the Drone, we already used automatic polygroup creation based on UV-coordinates or separated objects. But both methods won't work here because the model is made out of one piece and has no UV-coordinates that we could use for creating polygroups.
Let's see how we can solve this by creating polygroups manually with Polypaint.
If you feel unfamiliar with polypainting, you may want to quickly flip through Chapter 5, Texturing the tree with Polypaint again.