Your question doesn't make sense. Any manual loading order would be just that -
the order you import the images. Also, unless Flash has come out with some new
crazy feature I don't know of, you can't import into the library with action
script. You can import into the flash document, but that's not into the
library. If you are talking about not seeing a preloader until 90% of
everything is loaded, you probably have components on the stage. Flash loads
those components before it even gets to your action script, so by the time the
components are loaded, 90% is probably already loaded, and the remaining 10% is
what you have in your library. There are ways around that, but without knowing
more about what your fla document looks like, I can't suggest any solutions.