Zia in Altadena called the Bee Rescue Hotline when she spotted a swarm in her yard. It was suspended from a metal table and had been there for a couple of days.
Following Kirk's recent advice, I sprayed the bees with plenty of sugar water before nudging them into a nuc box; I probably sprayed them 6 or 7 times over the course of 20 minutes.
This made a big difference! Each time another bunch of foragers collected where the main swarm had been, I gave them a good couple of sprays, then waited a few minutes before scraping them into the box. The bees stayed very calm and nonaggressive the whole time.
I knew I had the queen in the box when I saw this line of bees headed up to get inside.