Oh, but you don't want to stay indoors! After all, Pokemon Go is a game of exploration, and harvesting hospitals for ghosts might be just a tad too morbid. Let's do some ghost hunting outside, but before we do, spend a minute Googling for reports of missing or dead children in the local woods. If you find any, head to the scene of the tragedy immediately, since it has been infused with sadness and is hence your best shot at finding a Phantump -- happy little trees possessed by the souls of children who were so lost in the woods that they died. But only children who died in the woods. Don't go looking for dead children in rock quarries, or children drowned in lakes. You need those primo woodland child deaths.
Speaking of children, Pokemon clearly have something against them, because if you're hoping to catch some Duskull, you're going to need to stock up on your supply of expendable kids to lure them in -- particularly the nasty misbehaving kids no one could ever love. According to lore, Duskull wander the night, "spiriting away bad children." They're like Santa Claus, except replace the lump of coal with kidnapping.
"What, you think skulls just grow on trees? No, you have to hang children there first."