Keep at it. I had the exact same questions/issues, except that my problem was getting out of my toe side turn into heel side turn. I catch edges there alot and bam, eat shit.
I basically had what snowolf wrote out for you here memorized and keep repeating it to myself. Once you're out on the slope, it is very easy to forget everything. Try to read it over and over again, watch his videos too, helps alot.
Also, someone here also mentioned to assign numbers to each step, I find that very helpful as well, as to making sure I don't rush through the steps. I tend to want to get out of my toe side as soon as i can because I'm not comfortable with it, and neglecting to get my board completely flat before going to my heel side, and eat shit this way.
My other issue is purely the fear factor, I dont like the feeling of bombing down the hill with my board flat, and my body sometimes would refuse to go flat, but it is an essential step before you can make edge changes.
Good luck and don't give up.