Did not find this in some brief checking, so I'll toss it here with apologies if I overlooked the tip elsewhere.
For layered parts, I have known that one could simply highlight the entire stave and then hit shift "up arrow" or shift "down arrow" to change the direction of stems in the entire stave before layering the staff. (i.e. stem up for the soprano, stem down for the alto, etc.)
Had not realized that the same could be done to change all tie and slur directions for an entire selected staff in a single step, prior to layering. Simply select the staff, right click for properties, go to the "notes" tab, and select the slur and tie direction (upwards for soprano and tenor, downward for tenor and bass).
duh!