Your friend: Do you celebrate Halloween in Russia?
You: Yes, we do. And is it your favourite holiday?
Your friend: Yes, I like Halloween very much because it is a holiday for children.
You: What do you usually wear?
Your friend: We usually wear costumes of wiches and ghosts and go to the peoples houses, shouting (trick or treat!)
You: What was you wearing last Halloween? (я не совсем согласна с таким вопросом, но раз в ответе употреблено именно Past Continuous, нам остается подчиниться. А вообще я считаю, что здесь должен быть Past Simple, т.е. What did you wear last Halloween? и ответ I wore a skeleton costume.)
Your friend: I was wearing a skeleton costume.
You: Did you tell ghost stories?
Your friend: Yes,we did. We were telling ghost stories and playing games all evening.