I have had poor luck with duo and various other popular lash glues because the inner corners simply do NOT stick and always come off. I have gone from wearing lashes once or twice a year to wearing them everyday now thanks to this liner.
I would recommend curling lashes 5 mins after applying. It helps stick the lashes to your natural lashes and it secures hold. If the inner corner or outer conner becomes loose after curling, its easy to just add more liner and stick down. If going for the black liner, I recommend using your usual liquid liner and then going over the lash like with this liner. This pen is too fiddly to get a sharp, neat wing.