Push multiple objects at once

With the regular Firebase JavaScript SDK, you can accomplish this with:

var updates = {};
updates['/symbols/'+ref.push().key] = {
  typ :"symbol1", ....
};
updates['/symbols/'+ref.push().key] = {
  typ :"symbol2", ....
};
ref.update(updates);

Since AngularFire2 is built on top of the normal Firebase JavaScript SDK, they interop perfectly. So you can just use the Firebase JavaScript SDK for this operation.