The whole theory behind 'blind bale' practice is based on the generally accepted fact that the human mind can only really focus on one thing at a time. Therefore, Once you step up to that target, whether it's a paper spot, 3-D animal, or wild game, all your focus has to be on your intended impact point. You cannot divide your attention by running through your shot sequence, or thinking about your grip, anchor point, or back tension. Your form has to be imprinted on your muscle memory so that it happens without giving it a thought. That's what 'blind bale' practice is meant to do. Therefore, before you can practice on the blind bale, you have to know what each aspect of your form should feel like so that you can "Focus" on each aspect in turn while shooting 5 or 6 arrows. The best way I know of to get that basic 'good form' is by going to a good coach. While the modern shooting DVDs can be helpful, I don't think they can replace a one on one with a coach. Assuming you've been coached so that you know what each aspect of good form feels like, now you use the 'blind bale' practice to imprint them into your muscle memory.For example, your bow hand must be placed on the bow exactly the same with every shot, and it must be absolutely relaxed throughout the shot. Most shooters I've watched will tighten their grip with release, some ever so slightly, some go white knuckles. So, with your bow hand placement set, you set your hook, and draw with eyes open to be sure you're pointed at the bale, then close your eyes and focus all of your attention on your bow hand. You don't think about your anchor point, nor your back tension, nor your release. You just feel your bow hand and make sure there is absolutely no tension in it at all. When you're sure there's no tension there, you can let the release happen, but your focus must remain on your bow hand to insure that you don't flex any muscle in it in even the slightest way. I think you'll find that this will take some practice before you'll begin to be able to keep all the tension out of your hand throughout the release. Once you're satisfied that you're keeping all the tension out of your bow hand, you can move on to the next aspect of your form, perhaps anchor point, or......?? I would recommend that you shoot no more than 5 or 6 arrows at a time, before retrieving them. As you can see, to do the blind bale practice effectively, you have to know what constitutes "good form" so that you're imprinting the best form that fits your body structure. If you have any Q about anything I've mentioned, don't hesitate to email me or send a private msg. As you can see, a description of this type can get very lengthy. BTW, I was very fortunate to have stumbled onto a week long archery academy early on in my shooting career, and had intense training by some of the finest shooters and coaches in the USA at the time, several of whom were Olympic medalists, and/or Olympic coaches.
Good Luck!