If you're able to use new construction cans, you could clear out the space where the light can will go from the attic space first, cut the necessary hole, install the necessary wiring, can and then pack the insulation back. All the work will be done inside the attic.

The location of the hole could be marked out from below using a long screw.

If retrofit cans are used, the hole will be cut from the underside of the ceiling board. You could use the resultant disk to push back the insulation, but there will be spillage from pulling the wiring as well as cutting the hole.

The cans have to be rated for direct insulation contact.

Thank you, David. I have to use retrofit. And, I guess I will just have to deal with insulation spillage!

If you have attic access, drill a 1/4", or so, hole at the center of where the fixture will be installed. Insert a dowel rod, or something, that is a foot or more longer than the insulation is deep. Then go to the attic and look for where the dowel rod sticks up, brush the insulation away, and then brush it back around your direct insulation contact fixtures after installation.

Painting the dowel with a bright or reflective paint might help you spot it.

Oh, that's a great idea. I'm not sure if I can get into the attic, or not. I think I'm going to have to install from inside the house. I like the idea of painting the dowel to see it! and I can see how that would help.

If you can get into the attic, new construction cans could be used. The process will be laborious and could be sweaty (unless done when the attic is cool).

However, the process is feasible if you're doing it yourself (assuming you know your way with electrical wiring, safety precautions while clambering around on ceiling joists in a possibly dark, hot and cramped environment)