Hey Bluedane.
Alex is right that without the verb it would sound very weird. Maybe I could record a portion of Traveller without it - I am sure it would sound extremely bad[:)] But hey, that's why we have reverb. You don't set an orchestra to play in a totally dead room either, for the same reason. I can't help you much as to how to make it sound big, but I can say that I generally use two presets, one for strings, percussion, harp (and possibly woodwinds), and another for brass - thats how my general routing is when I compose. I record a few more takes often when I mix it down in the end, but I don't do each and every instrument on its own. I would always do stuff like snare drums and cymbals on their own though, to get a lot of distance in the sound which I don't apply to many other instruments. The cold facts from my Lexicon MPX1 which I use on strings, percussion, harp, woodwinds are (these parameters may vary on your unit, so it's prolly not a big help): Size 34 meters, diffusion 100%, predelay 6ms, decay 2.13s, high-cut 1.6khz, shape 51, spread 24. On the MPX500 they are Decay 1.65s, HF rolloff 3.1khz, predelay 30ms, high-cut 4khz, diffusion 75%, size 50m., attack 10.
If you have the same unit(s) you could try these numbers. Then you have to find out the wet/dry ratio by using your ears.
I also used the Realverb Pro on the UAD-1 DSP card on "The Traveller" and the "Danny's Nightmare" though - for woodwinds and trumpets, and on some of the percussion.
But yes, it's not all because of the reverb - balancing, expression, dynamics and panning are the most important aspects in reaching higher realism.
As for "the big brass sound" I assume you're mainly referring to the 2nd part of "The Traveller" - here it's mostly orchestration, since I double trombones with horns - and trumpets, even in the low registers, which creates that sound.