Here's a trick to help find the short without wasting fuses. Wire a 12 volt
incandescent bulb in series with the fused load. In other words, one side of the bulb comes off the fuse and the other side connects to the line heading off to the devices. A tail light bulb in a socket with pigtails will work fine. Next pull all the bulbs out of any lights that are on that circuit, and switch all switches off then power up.
If there is a short to ground the incandescent bulb will glow full brightness but the fuse will not blow. Start disconnecting stuff till the bulb goes dim or goes out to isolate the short. If the bulb initially does not glow brightly start switching stuff on till it does, that load will be your short. A motor load will fool you though, it will look like a short.
I once had a camper with a roof rack screw driven thru a wire from the factory. It would blow fuses occasionally then finally got to the point where it wouldn't stop.