Originally Posted by
mechBgon
Silicone grease would be my first choice for the shifter internals. An auto-parts store will have it.
+1 Silicone won't damage the plastic shifter internals and I think "Jonnisnot" was a silicone based lube. Hardware stores also usually have silicone grease in the plumbing section.
I also agree on determining the source of the friction by checking each component separately.