Well, im in the same boat, idk how to get it to spin that long but i can get at least a few seconds, and enough to whip it back, but the biggest thing i found is that you really have to keep your finger like, loose, bend it at your first knuckle, i even think i have to keep it “looser” because i often get stuck on the inner rings and it spins out, also, keeping the string out of the way, because its so dumb when it catches and it tightens on your finger so tight. At lastly, my arm gets thrown out after like 10 minutes of practicing this, idk if you will have this issue but it made my arm srsly tired, and ive had pretty hurting shoulder for some time D:
OH! on more thing, when throwing the horizontal throw, if it gets 100% flat, ive found it harder, ive always had better luck with a slightly tilted throw, it will fix itself once it gets on the finger.
Idk man, i think hes magic though