squeaking brakes

[Slamtry]

I recently changed the front pads on my '91 Classic and they have been
squeaking under light braking ever since. I first tried some stuff I
bought in a local parts store for $2 which had to be spread over the backs
of the pads. This stuff turned out, when I took a closer look, to just be
brake grease. It worked only okay, cutting out about 75%  of the
squeaking. When driving in traffic, the brakes would start to make some
noise. I assumed this was because the brakes would heat up and the grease
would become less viscous and "sticky."

Yesterday, I pulled the pads, cleaned them (brake cleaner, natch) and
installed some different stuff I bought at Pep Boys. This is a thick red
coating that dries to a rubbery finish. Unfortunately this stuff works
even less well than the grease did.

So my questions are: is there anything that actually works? Do I need to
buy shims? Will that do it? If that is what I need, are they a standard
item or do they have to match the particular pads I am using (which are
metal masters I believe.)?

Dan