Yes. Most people forget about this. All contact surfaces should be cleaned, then greased. I do mine every 6 months and have never had brake squeel on any car.
I use a flat file to clear off the hard dirt from the upper and lower running surfaces. I also clean the retaining pins to a high polish. Copper slip all this including the back of the pad to
help absorb high frequency vibration (the squeel). It only takes 10 minutes per side and you can feel the difference in response even after 6 months of build up.