Someone asked for pictures a while back, so here it is: printrbot metal plus spool rest with UMHW tape. It’s just this: http://www.leevalley.com/US/wood/page.aspx?p=32182
(Well, the version they were selling about 10 years ago, which is somewhat thicker. No doubt also available lots of other places)
If it works on this cardboard reel with frayed edges, it should reduce friction for pretty much everything.
