Unless you've established a mentor-student or teacher-student relationship where said person is actively seeking advice from you, then you should ask if someone wants advice. The reason is because it's important to keep the control in the person's hands. They're a random person in Duty Finder. You and they will probably never meet again. When you say something like "I'm going to school you" you are disregarding any experience the person may have and setting yourself up as the ultimate authority. But that person does not have to see you as an authority.

Someone might try to call it sugarcoating or hand-holding, but that doesn't change the fact that it's essential that the person maintains control over whether they want to seek out advice or not. If they don't, then you may just need to exit yourself from the situation. Or grin and bear it until the end and then leave, having gotten what you came in for.