Mazda - 16 2.0 Driving an automatic car - Runfer D'Hills
If it is a true torque converter box, holding on the brake will be fine. In my Merc it even has a "hold" function which is set by pressing hard on the footbrake and then releasing it while in gear. Car won't move, roll back or creep forward until you touch a pedal but is still in gear. I think DSG type boxes dislike being held in gear.