I have used Ferr-L-Tite blue to place brass inserts into carbon shafts. Works great! How well is the "blue" when gluing broadheads to steel adaptors?
I've found the blue to be a little lacking in all applications, I'd go with something else.
I use the cool flex for inserts but prefer original Ferr-L-Tite for gluing broadheads to adaptors. I find the cool flex needs to be reapplied after aligning broadheads with heat.