brakes

ok soo i put new brakes on my 1999 300m about 8 months ago (the new onse squealed) and then put new rotors on at the beginning of summer because the were warped and shook when i stopped and about a month ago i just put new brakes on agian (and they squeal too). heres is my problem i can not get these to stop squealing the weird thing is they do not squeal every time i brake but most of the time and is very loud. so about a week ago i tried this stuff you spray on the back of the brake and and it is supposed to stop the squealing. the first set of brakes were semi metalliac and the second are ceramic. anyone have any idea on how to get them to stop squealing it is driving me insane.

Have the rotors turned and buy a set of NAPA adaptive ones or Wagner thermo quites. It is quite possible that the rotors are glazed and this is causing the squeal. having the rotors resufaced will remove the glaze and likely stop the squeal.