Rebuilding calpers, how do you the dust seal into the caliper (Nissan)

It's been a while since working on your type of vehicle, but the standard method I used was to seat the dust boot completely into the grove of the caliper, then used my fingers to expand the boot while manipulating the piston into place (tricky? yes, but not impossible). If it was particularly difficult to do, then I'd slip the dust boot onto the lower end of the piston, then fit the lip of the boot into the seating grove on the caliper (make sure all of it is in position), then work the piston into the caliper, which would help to seat the dust boot into it's grove. Once the piston is seated completely into the caliper, I'd use a small slotted screwdriver to make sure the dust boot was seated properly to the piston.

I don't know about that specific caliper, but when I did it on my Oldsmobile, I put the piston on the back end (inside) end of the piston first. It isn't in the groove at this point. Next, work the other end of the seal into the groove in the caliper. Then press the piston into the caliper with an even pressure, using a C-clamp. When the piston goes in far enough, the seal will snap into the proper groove on the piston.

Good luck.

Use the required tool also, someone else. With the boot installed in it's groove on the caliper, it's easier to use 2 hands to expand the boot & have someone else drop the piston in. Good luck.