Lower control arm pin

Leave the "shaft" in the crossmember.
Take the control arm off the of the shaft.
Get out your vise grips, channel lock pliers.
Put onto the shaft, in a non marring location.
Tighten down the self locking nut.
Reinstall the LCA, onto the shaft.
Easy peasy.

It's the same principal, but in reverse, if you were at a wrecking yard, pulling LCA's off some donor car.
When the LCA bushings are so shot to hell, you can't get the nut OFF, because the shaft is spinning around due to the shot bushing.
You pull the LCA back off the shaft, tighten down your vise grips, remove the nut from the front threads of the shaft.
Done that, many times pulling LCA's off cars at the Pick-N-Pull's.

But, here's another FYI here for you.
I always have found plenty of room to tightening or loosen the nut on a LCA by using a pair of vice grips by clamping down on a shaft in the car, by going up between the the back side of the cross member, and the LCA itself, when removing them.
You can do the same on installation, tightening down the nut.
Take a look at your car, and you will see what I'm talking about.