Also, don't use any lube that isn't SPECIFICALLY made for brake glides and calipers (I don't care how many years your uncle's been using mutton tallow on his Buick.

)... Anything not made for the purpose is just BEGGING for a frozen piston or caliper glide.
As previously mentioned, if the pistons or the glides are pitted then replace them. You can get away with cleaning and sanding the glides until no roughness is encountered (start with 400 or 600 grit and move up to 1200) but I really don't recommend it for any purpose other than to get you by until the replacements arrive.
Make sure everything is well lubed and sliding freely.