I have 2 different pinking blades. One has the "normal" pinking one would expect, the other cuts a more curvy pinking design. Both took a bit of practice for me to get right. Now I really like them both. And yes, they do help keep fabric from fraying so much.
I would suggest that you start with an old ruler or straight edge....even a wooden yardstick .... and practice a few strokes using that before using a good ruler. You have to hold the blade vertical....don't let it lean over into your ruler.
Also...for me, cutting curves required a bit more of my attention.
Practice is good.
Have fun.