DS is the only major library with individual singers where you could theoretically humanize notes off. Just about every other library out there has all players release at the exact same time (though you can humanize a bit with LASS too). What I do to combat this in other libraries is bring the modwheel down a bit at the moment of release. Players tend to do this naturally. Especially in expressive lines, it sounds good to have the note fade almost completely away before the release.
As for a practical way of recording each player releasing at different times, I'm not really sure about the best way to do it but I'd imagine your own personal workflow would affect how you would go about it.