You should wait until the car is completely assembled and resting on its own weight before tightening any bushings. I usually drive them around a few feet before tightening, or at least push it back and forth to get the front suspension to roll into position.

On the lower ball joint boots I use 2 pair of channel locks to get them on. Sometimes they are a bear and you have to be careful not to tear the boot. There is doubtless a better way. I just dont know what it is.

I line the notch up toward the inside, hold one side down, and then pull the other side down, then I work the pliers around to get it fully seated.
maybe if you warm it up somehow first it could help (?)