It is a little known fact that there are staff "witches" that are paid to bless one out every one thousand Ouija boards coming out of toy and manufacturing companies. That is at least the ones from America, the UK, most of Europe, and Russia. The Chinese ones are just pressed cardboard and a silly shaped plastic widget thrown into a box. Of course, most of the time, whenever one of these keyholes to the Other Side appear in a Crawlspace game, it'll be one of those rarities. If the Characters have any sense, when they see a Ouija board they will run like hell into the backdrop and hope to be murdered by Bigfoot or be abducted by aliens.
It is amazing how many people worry about random folks that they encounter on-line, but have no qualms about popping into chat rooms for the dead and demonic on a lark at a party. In the universe of grade B horror flix, there are as many "trolls" on the other side of a Ouija board as there is in an internet forum about upcoming superhero movies.
The GM/Director can use the Haunted House random generator to develop a random spirit or two when needed.