I like injecting for pork butts, the Weber "Smoke" cookbook has a quick and easy recipe for injecting pork. Brian's right, fill your coal ring and then light some up, and you're good to go. Don't worry about using too much charcoal since you can close the vents after your done and save whatever coal is left. My personal opinion is the more meat you can fit in your smoker no matter what size, the better the smoker works. I've done single pork butts, 2 pork butts, and just last weekend 4 pork butts (almost 40lbs) on my 18.5 WSM and the last one was the easiest and least fussy. I was able to literally just load the WSM, set my vents, and forget it for 13 hours. In fact the smoking was done overnight and I slept through the first 8 hours. The pork turned out great.