Here is an approach I have used successfully. Pull the fuse and connect a 12 volt bulb across the fuse holder. A car headlamp is a good choice. Have someone watch the bulb and go around the tractor and wiggle wires, harnesses and connector. Tap light bulbs, etc. Of course the bulb will flash or flicker or brighten when the short happens. This will help you find an intermittent short. It may help if you pull all of your light bulbs before doing this. I would leave the bulbs in at first.
Given your description of your blown fuse, it sounds like an overload. In this case put a current meter in the line and monitor the current. If it exceeds the fuse rating, or even close the fuse can blow over time. Even overloaded a fuse can last for hours. You may not normally run it long enough to make it blow. The fuse can age quickly if overloaded and just fail from being marginally overloaded for accumulated time. If this is the case it may be the wrong bulb(s) or you may have to run a separate circuit for some of the loads.
Sorry for being so wordy. I hope this helps.