In the lost Grove Temple how to perfumes work do I just walk around a room or do I need to encounter them with the battle sequence?

You just go from room to room and trigger the battles. You can farm in endless mode once you clear the dungeon floor - in Temple the rate of Sylesti varies by floor if I remember correctly, so higher level floors have higher chances of Sylesti encounters but they're a lot tougher to farm/use for training.