The saddle has ball oilers on each side- the front is easy to lube, because it has a gap at the peak of the Vee way. That gives the oil a place to go, and it dribbles down from there.
On the rear way, I could never pump much oil into it- it'd just spew out of the ball check. This is almost certainly because the way has worn smooth- there's enough "stiction" in there that I can't generate enough pressure with the cheap oil can and poor oiler seal to "lift" the saddle from the ways to inject any oil.
The fix was kind of brutal, but necessary- a quick blast with an abrasive wheel in a die grinder:
The grooves don't cut down the bearing surface by any appreciable amount, but give some room to pump oil in, and as a "reservoir" to hold a bit of oil as the saddle slides along.
Considering the lower bar is steel rather than iron, I might do something similar rather than trying to scrape it.