The image you used as an example already has some nice shallow depth of field from the beginning, which I think really helps make blend the effect in the end result. Did you try applying the effect to an actual selfie, which usually has more even focus?

One "clever" idea someone had was the use of the depth camera on the new iPhones to isolate the subject.

Rather than using a hardware solution, this is a good software solution that can be accomplished on more devices.