Apply the grease. It's the other part like pins etc vibrating not the pad scratching the rotors causing the squeals.
If there is a backing plate....check that too. Btw, mine it squealed like a pig for a year.
Visited 5 workshops which tried everything from bedding in for you, chamfering the edge of your pads, cleaning the caliper.
Finally I downloaded the schematics and found that the backing plate is directional. Disassembled the caliper, took the plate .... Clean it and found a little arrow etched on the surface of the plate. It is suppose to point up. It was pointed down as the last servicing.
Put the plate back and applied a bunch of grease on most of the parts except the pad and rotor surface. Then the squealing finally stopped. Lasted all the way till I sold the car. It was a Brembo but BMW perf brakes also made by Brembo.
Go disassemble the caliper and have a good look and apply the grease. Don't miss the dust covers / caps etc .....