In most "traditional" brush technique, the snares are disengaged. The batter head is tight, but not the "tight as I can get it" tension that many current players use to get a sharp attack. The resonant head is fairly tight (to allow for good snare articulation when the snares are engaged.
I normally try to get the snare (with snares disengaged) to provide a melodic interval with the toms (I used 3rds, 4ths or 5ths - depending on the shell sizes, etc).
Naturally, the size and material of the snare shell, the type of batter head (I prefer a standard Remo coated Ambassador for brush work) and the type of brushes all play into the final sound.
Good luck with you session!