I never lube behind the shim as it makes it slips of easier. I only apply lube to the caliper pins, below the abutment clips and on the caliper's piston.
I use CRC Silaramic under the clips, on the ears, and on the shims/pistons. Have had the same front pads on my CX5 for 5 years with no issues. Also worked well on an 02 Tundra.
This grease is very thick so it stays in place well.