I've never bothered with shims on any car and never ever had squealing brakes.
As wooble says, with calipers in good order and a bit of copperease on the back of the pads (and on the sliding edges) brakes just don't squeal.
Whenever I have had any kind of noise from a brake it's been because of worn out pads, sticking piston, rust or debris getting trapped, or pads not seating properly because of a wear ridge at the extremity of the bearing surface.
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