I've sprayed various trees with diluted alcohol before. In summer time there were almost no problems at all because it evaporated as soon as it did its job. In winter, however, I started losing trees because of it. In SoCal your experience may be different, but be careful.
A q-tip with alcohol is very effective for killing mealybugs one at a time. Just a tedious way to go about it.
Usually in winter I spray with a tobacco tea. Kills anything with a nervous system, a little bit of discoloration occasionally, highly effective. This year I'm avoiding it, though. We were able to collect some wolf spiders and ladybugs for the trees, so I'm hoping to see how good a job they do.