We resolve the real-time dynamics of a purely dissipative quantum spin or, equivalently, hard-core boson model on a hypercubic -dimensional lattice. The considered quantum dissipative process drives the system to a totally symmetric macroscopic superposition in each of the sectors. Different characteristic time scales are identified for the dynamics and we determine their finite-size scaling. We introduce the concept of cumulative entanglement distribution to quantify multiparticle entanglement and show that the considered protocol serves as an efficient method to prepare a macroscopically entangled Bose-Einstein condensate.