I find that holding the joint together with a large pair of pliers will put enough friction on the ball stud (that's what sticks out) to hold it in place while you put the nut on.
Again - this is important. MAKE SURE YOU WIPE ANY NEVER-SEEZ OFF THE THREADS! Due to the lower friction offered, you will SERIOUSLY overtorque the nuts if you have enough on there to be a problem, so be careful!
Alternatively, if you get some on the threads and leave it there, reduce the "book torque" by HALF - because that's specified for "clean, dry" threads.
5-90