An aileron roll is a positive 1G maneuver, so pouring the liquid is still possible
.
Never heard that before. I know when I do an aileron roll it is defintely goes through -1g or thereabouts !!!
I was taught, pull up about 30 degs (> +1g) , centralise all controls, then stick hard left or right (< 1g) and hold it until until wings level, then centralise again, recover from the nose drop after wings level (> 1g).
A barrel roll on the other hand goes a bit like this.....30 degrees of heading off where you want to end up, nose down to accelerate to entry speed (if nescessary) then back sick (>> 1g) and aileron...In many books it is classified an advanced maneuvre.....