A device similar to chorusing is to layer the horn lines by doubling the part on another track and then offsetting that track by one or two ticks/clocks by using Edit -> Track Shift.

I often fatten horn parts by copying the original track onto a second track, changing the channel, offsetting the second track using Track Shift by 1 or 2 ticks/clocks (i.e., 1 or 2 ticks later than the original track), and assigning a *similar* but not identical horn patch to that part, a patch with a different horn *texture* (some of the patches in the XP have several variations).

Often a generic patch from the GM bank is perfect because those patches are generic enough not to take the blend out into outer space but different enough from the patches in the preset banks to add different timbre and texture.

The different texture/timbre and the slight offset considerably fattens up the part. I use this on strings as well; in fact, all the time. I call it "shadowing" a part.

You need to experiment with blends of different patches and offsets.

Good luck.