“Ocean/Sky/Great Heart Breathing”
is Michael’s complicated name for Blissful Breathing Qigong.
It is a qigong form that contains the components Ocean Breathing, Sky Breathing, Great Heart Breathing, as well as other components that are not these.
However, to answer your question, I would recommend just the Ocean Breathing itself.
It is more focused on the lower dantian and getting into it deeply.
Blissful Breathing Qigong is a nice form, but I see it more as an energizing, rejuvenating form. Not that that is bad, but it has a different flavor, and is not as best suited to your desired needs.