Calibration is as simple as making a program that goes through a range of retract lengths/speeds and visually verifying that the flow indeed does stop when the nozzle is floating in the open air and that the flow starts back almost immediately when you go to extrude again. I wouldn't try anything fancier than changing the retract lengths and speeds. It is my experience that you can find values that will make you more than happy and those are easy values to mess with. (I have a .4mm nozzle and I use 5mm retract at some speed I have forgotten. The tube is somewhere on the order of 600mm long.)
Additionally, Slic3r has introduced some features that are suppose to make bowden printing easier. "Wipe" is something to check out among other things. A google search for "Slic3r settings for a bowden setup" will also give you lots to think about.
Additionally, Slic3r has introduced some features that are suppose to make bowden printing easier. "Wipe" is something to check out among other things. A google search for "Slic3r settings for a bowden setup" will also give you lots to think about.