Alex, pea sized blobs of polish, max. 4/5 of them around the pad and on in the middle. Then dab the pad against the paint until it has a decent spread.
The stages of polishing depend on machine, but for a DA start on speed 2-4 for a decent number of passes to spread the polish. Then move up to 4-6 for correction. Zenith technique is great, but doesn't always work on DAs. In fact, barely ever works in my experiences with hard paint!
(zenith is speed 2, speed 4, speed 6 and back down again to correct any minor marring the major correcting has caused).