2D Mirroring animations not working. Unity 5.

Hello there, I have been trying to figure out how to mirror my animations for days now. The mirror checkbox doesn't seem to do anything, and changing the scale from 1 to -1 isn't an option either since the tutorial i'm following relies on a transition from left to right and with a change of scale, the transition happens gradually causing my character to scale thin until facing the other direction. (if that makes sense...) (This tutorial - https://www.youtube.com/watch?v=XZDjkQ8wEd0 ) I Would just like to know if there is a possible way of mirroring the animation preferably without code. I am animating in the unity animator; mecanim i think? But even if there is not, maybe somebody knows a good outside program (free since i'm low on the old funds) that can animate smoothly and isn't a pixel art program.

So in a nutshell, How can i mirror my 2D animation from running right for example to running left without changing the scale?