How can I create realistic sounding string sections in Garritan Personal Orchestra 4?
This question needs a bit of expanding. What program are you using to play the Garritan Strings? I can describe a bit of what I do in Finale. Other programs may be similar but differ in details.
I (of late) like to use the Convolution Reverb provided in the Aria Player. I generally get the music (at least some of the themes, arrangements, and orchestration) and listen to various reverb settings. The big concert halls do sound good with string sections. (Solo strings are a bit different.) The Garritan manual for GPO4 has a description of how to use the contained instruments.
I (earlier) used the Ambience Reverb in Finale which can be combined with the Convolution Reverb (several corresponds on the Finale forum do this.) I use the "dry" setting to get loudness (direct instrument to mike) and the "wet" setting to give a "woody" or "echoey" sound (echoes from the walls before hitting the mike.) There are other settings, but I rarely adjust these as I'm not really familiar with using an equalizer. I do use panning to give some width to an ensemble.
You can just play around with the settings. There are several posts on the Finale Forum (Make Music) the Garritan Forum (also Make Music) and I'm guessing some of the more electronically-oriented forums about settings.
Supposedly, to get good results, one should tweak things in a DAW but I've never done this.