Personally I put a drop of light machine oil on the lead screw just above the Y gantry between prints, while the head is down. When it prints, the lead screw raises the gantry and the threads spread the oil.
If I was going to do a really tall print, I'd consider adding a little oil higher up the lead screw too where it rarely goes.
A Y axis lead screw is a ...
I always used electric guitar strings. They are 0.05 mm smaller than the nozzle and because of the texture it scratches off any material that is stuck. Plus since it's not hard there's is almost no chance to damage the nozzle