Start with the roughest files, then go to rough, then finer sandpaper. At each step, file or sand until the previous grit's scratch marks are removed. Lift up when you pull the file back. Please call me on weekdays at my work number, 581-5020. I keep my sources on my PC in the office and will be glad to help you figure out what you need.
Teeth are the only permitted tools.
Put successful creations in a zip-lock bag and bring to school for show and tell. Surprisingly, teenagers do this best, if they can stand to get their faces messy.