Hi Matt,
Well, there are quite a few ways you can do this. It all depends what your "wall of sound" involves. You mentioned "modern" in your other thread, so I'm going to assume you're talking guitars being the wall of sound with other enhancement instruments? I'm hoping I'm correct there.
There are a few bands that do this really well with keyboards being involved. It adds that little extra power going on. The other way to do it is with a few guitars. Some playing octaves, some with a haas effect or even a slight chorus effect with panning being the thing that fills up the holes as well as different sounds with a different eq curve. In my opinion, the use of compression isn't the key here. It's all in the sound placement as well as the sounds themselves creating the wall.
For example, Good Charlotte had a tune called "I don't wanna be in Love" that was awesome with layering and that wall of sound. They added a load of guitars and keys that made the tune incredibly rockin' yet with this awesome dance feel to it. The layers on that tune as well as the quality still blow me away today. It was a great use of keys and heavily driven guitars. It never quits and bombards you with that wall of sound.
Another band that did this rather well is a newer band called Escape The Fate. They do a song called "Gorgeous Nightmare" which has this same type of vibe to it. You can check out the song here:
http://www.youtube.com/watch?v=om2K8PP0OJE I had a client come to see me a few weeks ago that wanted to cover that song. We were unable to find any backing tracks for it at this time, so he made me record the entire thing. My version isn't quite done yet, but I want to share it with you because it's not done yet.
In their version, you hear keys and sound effects all over the place. I haven't done that yet other than the farty bass sound which I'm not done with either as it needs more decay and a real bass will be added to it over top. I have a load of work to do on this song (as well as the gentleman that is going to come and sing it) but my reason for sharing it is, listen to the guitars on the pre-chorus and chorus parts. The layering here is what I *think* you may be after. You mentioned Muse and how they were just using 2 guitars, bass, drums etc..and this in my opinion, is a good representation of that considering how stripped down my version of this song is right now.
It's 2 guitars, synth bass, drums that I played on my V Drums kit using Steven Slate 4.0 and 2 more rhythm guitars that come in during the pre's and the chorus. If something like this is what you're after, let me know and I'll explain the process to you, ok? Here's the link to my unfinished mp3:
https://dl.dropbox.com/u/4909348/DannyGorgeousNightmareMaster16.mp3 It's raw, so forgive me...but for as raw as it is, I think it came out pretty good at this point even when I compare it to the original. Once I add all the right stuff, tweak the mix a little and add some room so it doesn't sound as direct, this is going to sound pretty cool....at least that's what I'm hoping. :) But the guitar layers almost give you the impression that a synth was used if you listen close. Yet, the only synth is the farty bass sound. Now imagine some good synths over top of those guitars in a higher key like they did in theirs...it's going to build up really nice. See what you think...and like I said, if something like that is what you're after, I'll share how I got it. If I totally blew this and misinterprated what you were asking, please accept my apology for wasting your time brother.
-Danny