I've never dipped rosemary cuttings in rooting powder just cut, remove some leaves and straight into compost. Never fails.
I agree about the cutting back to hardwood, always ensure there is evidence of a leaf bud or small sprig. We cut the dentata back very hard after the heavy frosts last year and it is back to the same size as before.
I've never pruned the rosemary. I've tried to cut it into shape a number of times but it still grows haywire just like the bay that I've also tried to cut into shape regularly.
Bayleaves anyone
Time it right though as you don't want the new cuts to get frostbitten.