Hi,
I've not tried them, but looking at the description of it and some others, the idea sounds OK. Maybe try one of them, and do a little smoke pencil test on a windy day.

We had a lot of leakage through IC rated can lights. I went into the attic and pulled away the insulation around each, then sealed up all the open holes with aluminum tape, and then sprayed the polyurethane foam in a can ("Great Stuff" is one brand)to seal the area where the can joins the sheetrock, and any other places that seemed like they needed it. Then put the insulation back in place.

This works 100%, but its more work. Not sure if its technically legal, but we use low wattage CFLs in the cans anyway, so not much heat.

Before doing this, on windy days, you could just feel the cold breeze coming through the cans -- it makes a world of difference. Its depressing to think that such awful designs can be so common even in new construction.

Gary