something wrong here. either someone isnt communicating very well with you about some additional work your car needs, or they are about to take advantage of you. there is no lubrication work that will stop brake squeal. the problem will persist and is due to the composition of the brake pads. since introduction of new materials to replace asbestos in brake pads, squeal is just a way of life. if the brake repairs done to your car were properly carried out the squeal should be intermittent, probably influenced by wet or dry weather conditions. live with it. if it were my car i would get it out of that shop, post haste. when the brakes get excessively noisy, apply them lightly at speed to resurface them a bit, the squeal should be at least temporarily gone after doing this.