Is putting a baby in a "duyan" effective in putting them to sleep?

Yes, extremely! Lulling them to sleep in a duyan is one of the greatest parenting hacks. But be sure to keep a close watch and not to put any choking hazards in the duyan with them; this includes soft pillows and blankets. If you do prefer to put padding on the duyan, make sure it's taut and fits snugly over it. You can transfer them to their crib once they've fallen asleep.