Squeeling usually indicates contamination on either the linning or drum or both. Contamination can be with break fluid, grease, oil or dust. I would do exactly as 60flattop says and checkfor leaking wheel cylinders, worn out/leaking wheel seals or some other source of contramination. When I was working in the repair business a 'break job' always included new or rebuilt wheelcylinders,new front axle seals as well as grinding the shoes to fit the drum. We were also required to keep everything scrupulously clean. Just replacing the shoes usually does not work out well.