Does anyone have any experience using meditation for preventing complex migraines?

Usually very helpful. Research shows that meditation can prevent migraines & reduce severity (though I do not believe complex migraines have been studied specifically). One study showed a 70% reduction in frequency by doing 1 hour of meditation & relaxation breathing 5 days a week. Lesser amounts are likely to benefit as well. See http://somebodyhealme.Dianalee.Net/2008/06/meditation-yoga-can-reduce-migraines-up.Html.
Abdominal breathing. Studies have shown that meditation can have positive effects on your autonomic nervous system, your immune system and your hormonal systems, thus rebalancing your overall metabolism. Proper abdominal breathing techniques are paramount in achieving the relaxation response. You do not need to be a master. Find someone who can teach you this and then practice it consistently.