The swarm is unitary--- no recruits after the initial departure.
The length of the bivouac is erratic. Watch for dancing on the surface -- as this ramps up, the swarm will soon depart.
I think the best time to hive a swarm is in the late afternoon, less likely to abscond. Avoid smoke (which will drive the swarm back out of its new hive) and scents, as you want the swarm pheromones to permeate.
Best way to hive a swarm is to just cut the branch off, you can even leave a bit of it in the hive (or cardboard box if no hive is available). The scent on the branch will draw stragglers.