Do the BJ have grease fittings or holes for grease fittings?
If you have grease fittings, then you would grease the BJ after you've assembled everything, including torquing down the steering knuckle.
If it DOES NOT have grease fittings or a hole to install one, then you have to follow the instructions that came with the BJ, to the letter and use any grease they supply. No instructions, no supplied grease, then use good quality grease and work it in with your fingers as you move the BJ around, build up lots of extra and put some on the inside of the boot before installing the boot.
In the past, on other vehicles, I pressed the metal ring dust boot onto the BJ with the same tool, and I used to much force and split the boot off the metal ring and it wouldn't seal.
Good luck trying to find just a dust boot, I have yet to find these as a stand alone item. Unless they are some polyurethane/rubber universal replacement, without metal rings that seal up the ends of the boot, the universals do work, but doesn't really seal well, you have to grease them often to displace any water that might work its way into the BJ.
Since then, some BJ, I was able to push the metal ring dust boot on by hand, a little difficult, but I got it on. Sometimes NOT, the ring is just too tight, I use the press tool to get it started, but DO NOT BOTTOM IT OUT, or you'll split the boot like I did, I stop short of seating it fully, then tap it on with a punch and hammer the rest of the way. Do it lightly, its delicate, it doesn't take much pressure to tear away the rubber from the ring.