I have been using an Equalizer hitch for about 14 years now.  When I got the first one, Progressive said it was fine to lightly grease the L brackets along with the pivot head.  They did not have the plastic sleeves yet.  I have done this since then and my hitch is quiet and I have yet to experience any sway at all.
That said, I avoid adding grease to the L brackets unless I hear some noise.  Even then I only add it to the head and that usually quiets things down.  If it doesn't, I will put a very small amount on the L brackets.  Usually have to do this only once a year.  The head gets greased about 3 or 4 times a season.