Spray seems to work for skunks, but anyone who is willing to develop the skills necessary to master rifle handling under threat, snap shooting, and shooting moving targets, should be up to the challenge of personal defense with a firearm if that is their preference. Provided that your drills have some relevance to reality, you will benefit from them. A little practice is better than none, but the first step is to understand the problem, then identify your deficiencies, and work at overcoming those weaknesses. Not everyone is good at self criticism, so you might benefit from the guidance of a good shooting coach. Some deficiencies can be resolved with just a little effort, and a slight change in technique. For example, when the pail accelerates rapidly towards you and you find yourself shooting behind it, that represents a pretty realistic problem. If we think back to the infamous canned lion hunt video of a few years ago (that's the one where the viewer was tempted to cheer for the lion and ignore the lessons that could be learned) we recall that the lion nearly won. When the lion charged, both the PH his clients shot behind it, due to the difficulty of solving 3 marksmanship problems under stress:
1) The angle between the target and the muzzle was constantly changing, as was the apparent size of the target,
2) The target speed was accelerating, which when combined with the first problem made estimating the lead complicated,
3) The target's trajectory moved vertically as well as horizontally.
The easiest way to solve this problem be it on pails, lions, or bears, is to lower your bullet's trajectory by shooting from a kneeling position. You can acquire the position very quickly and it puts the trajectory of your bullet on the same horizontal plane as the length of your target. Once you are shooting on the same plane as the target, there is no need to lead it, so the vertical displacement is the only motion you have to allow for. Some years ago in an old bear defense thread, Bone Collector recommended this technique, and although I instantly saw the wisdom of it, I questioned if in a real world, dangerous bear encounter, I could make myself use it. The problem is that when you kneel, you're anchored in place and can't move out of the way. Guess what, it turns out I can use it, and the knowledge that even when under difficult circumstances I can place my shot on target, provides me with the confidence to prevail. Thanks Bone wherever you are.