Partitions (gobos) will help to get some seperation but not total seperation. Space or seperate rooms (at least amps in seperate rooms) is the only way to get much seperation when recording a whole band. Close micing will help if the band is playing at pretty low volume. A good sounding room is critical to getting a decent recording as room ambience is part of the overall sound you will be recording. Sometimes the bleedover can work to your advantage when trying to get a more "live" sound. The main drawback to all at once recording is the band has to be very tight with their sound. Mistakes mean starting over, there isn't much you can do to cover mistakes on live or all at once recordings without taking something away from the recording. Once it's tracked, thats what you've got to work with so everyone has to get their part right or start over.