Dealing with a ghost defendant

Does anyone have any tips or tricks they like to use when a defendant is particularly hard to find? I’ve recently run into a few issues where a defendant won’t pop up on public data sites, they don’t have a license plate, etc. Are there any websites or companies that have proven useful for you?

I prefer to not file against John Doe or a wrong address, but sometimes doing that and ordering a skip trace is our best bet. Interested to hear what others out there do. Thanks!