So, the year is 1206, I'm a huge Zoroastrian empire in NK mode.
Would it be a good idea to switch over to feudal again?
Let me see if I understand correctly: You own all the counties in your country, but want to give (almost) all of them away to create a patchwork feudal state full of ungrateful backstabbers?
If so, what you want to do, is
a) try to get all the minor nobles of your dynasty (using the dynasty window, accessible on your char view) to move to your court.
b) get a small amount of money.
c)invite some nobles (all at once- they will get more expensive, once your income isn't ~0), don't worry if you don't have enough money to get a noble for every county.
d) assign counties.
d.1) Promote especially capable (and reasonably young) barony holders-
mineral planets church vassals are the best.
d.2) give counties to your dynasty members, including children and the elderly (unless they have non-dynasty heirs)
d.3) give counties to the people you invited.
d.4+) if you miscalculated the invited noble count (went lower), promote more barons.
e) unless you want to create a merchant republic (they're a great source of income once they get going, but very treacherous), destroy all but 2 duke titles you hold.
e+)if you do want a merchant republic, promote a coastal mayor and give him a duchy. (Any duchy will do, though he will be slightly more pissed if he doesn't hold any counties there)
That's it.
fake edit:Just in case this isn't obvious- this all happens while the game is paused.