I am a beauty therapist looking for a way to give an eyeliner effect when tinting lashes. Any tips?

Hi, I am a beauty therapist and have been asked by a client if i can give an eyeliner effect when tinting eyelashes. I do remember achieving this once, but purely by accident. I had thought about drawing a line under the lower lashes (with the tint) then closing the eyes to continue tinting the lashes. Any ideas most welcome.
Thank you,
Georgia