Best Whoas are taught on the ground
Preferably without a bit because honestly as a western rider I want a horse stopping without reins. It's sit in your pockets and verbal whoa and that tail better be tucked and I wouldn't mind a nice STRAIGHT pair of lines in the sand behind me.
Now to get that starts on the lunge line with all the other verbal cues. We do use back up a lot cause it's an easy way to get the but under and also it's for the ropers cause they want the slack taken off when they have a calf or cow on the string.