Armed with this new knowledge, today's cook went much better than my earlier efforts. I think the #1 trick is to crack the lid on the cooker if the meat temperature is failing to rise sufficiently fast. Another, albeit much less significant, factor pertaining to the charcoal may be the size of the briquets. I just realized that the charcoal I had been using is probably 50% larger than Kingsford. What this means is that when I fill the basket with it, I'm actually not starting with quite as much total charcoal compared with what I'd have using Kingsford: smaller briquets = smaller gaps = more usable fuel.
For those interested, you can see the photos I've posted on two other threads about skirt steaks and pork shoulder vs. Boston Butt. On the agenda for Memorial Day, brisket attempt #5 and a couple of whole chickens.