Helpful and sane? Well, at least we try to be HELPFUL!
First, let me say that I've (as a homeowner, I'm not a professional) always struggled with texturing...but I'm getting pretty good at it.
I think what the HD guy was referring to is something like using a broom to put texture onto wet "mud." This can look really neat (vertical striations caused by the bristles)--as can loads of other possibilities (obviously not the "ones" you chose.)
Here's my suggestion. Try to reduce the sizes of the mountains and depths of the valleys. You can sand the mud--but with as much as you have to do--pick up the texturing compound sandpaper built for the task (say, 100 grit). YOU PROBABLY WILL WANT TO GET THE MUD A LITTLE WET--TO KEEP DOWN THE DUST! If you sand a huge area like that without getting it wet, you'll have a heck of a lot of dust!
So, your goal is FLAT and SMOOTH (or at least SMOOTHER). Take the tops off the mountains--don't try and sand too much at one time. Then come along and mud the valleys. Doing a little at a time is much better than 'all at once'--don't "overwork" the mud.
As much variation as you seem to have, you probably won't get this perfectly smooth. But hopefully you can get it to the point where you can pick ONE of the textures and try to match it all over.
Texturing can be tough to match. Lately I've been buying aerosol cans of texturing (but this is a more conventional look, not the freestyle).
One point to your question--you asked "Do I just sand enough to get the major ugly bits out of the way and then RE- TEXTURE over it?" Maybe--but that "re-texture over it" clause scares me a bit. If you have a VALLEY, you can fill it in--but (from that question) I'd worry that you might somehow build the mountains higher.
Good luck, and if you think of it, take a digital picture of it and provide a link; I (or someone else) may be able to provide some ideas.
-k2 in CO
[This message has been edited by k2 (edited February 16, 2004).]