Answered:
Okay I cant say this with certainty as I am not you, but I think maybe the vibrations you are feeling are not the vibrations that are required to astral project. I say this because usually when one can feel the vibrations strong enough that are required to project it should be fairly easy to succeed in getting out. Getting to the hypnagogic state to begin with & getting the strong vibrations is usually the hardest part of all. If you can master that you should be able to master astral projection. If you are getting the proper vibrations, just visualizing floating out should do it. Or you can try many other methods (roll out, swing out, sink out, or the rope technique etc).

There are different sorts of vibrations that you can feel. Some vibrations are easy to feel during meditation where you feel like tingling vibrational energy all through you while youre deeply relaxed. You can also feel like waves or pulses of vibrational energy flowing through you. But the vibrations to project feel somewhat different. They are far more powerful & intense than these other vibrations. Idk exactly whats happening with you though. I think youre on the right path anyway. Keep experimenting with it & see where it goes.

EDIT: Oh also lucid dreams are a gateway to the astral realms. So thats another option, that doesnt require the vibrational stage at all..

http://www.consciousdreaming.com/lucid-d

Answered:
Feel where you want to go, and go there.

It is a lot like willing your arm to move (we move our arms all the time without thinking about it).