To be honest, it depends on the person. I think there's a thread here on the forum, where a couple of guys are finding it tough to go up to a girl and even talk to her, so for them the first part of your process would be ideal.
If you have a bit more confidence then directional or observational openers are less "all or nothing", giving you a chance to build a conversation.
Then once your more experienced then go semi or full direct, as you'll not want to be tied up chatting to girls who may or may not want to go on D2. My only issue with full direct is that it forces the girl to make a decision, there and then, on wether she hooks up with you, and you could lose a great girl straight away, wheras by establishing social comfort and then building attraction, your more likely to get her to see you again.