my best suggestion for you would be to first learn how to do a raley or a batwing and master the feel of loading the line and using the tension to bring you back down. It is pretty difficult imo to learn these by taking baby steps. I learned how to do switch OA 180s by taking baby steps and could never really get any good ones if I just tried to grab and then drift OA. It wasn't until I just really loaded the line and threw it way out the back that I figured out that the board will come back under you much quicker and smoother if you fully commit to letting the board go out. As far as just doing a grab I can't get it out behind me because I am trying to through the trick like a grab, versus my friend who can do raley's and 911's who throughs the trick more like a raley and can get them much more OA and pulls them in with a lot less effort.
So you can learn them by drifting out but I think that is a much more difficult route and will take you a lot longer to get them the way you want them.