In my limited dealings with the front top shock bolts on the TJ, I have found that a ratcheting box end wrench is the best way to tighten the nut. You can use a variety of things to hold the top of the shaft to keep it from spinning, but I think the main thing is to use the wrench to apply the torque via the nut, not via the shaft. Don’t ask me why, but it seemed to work.