I originally replied to this post on Snyder's website, but I'll repost it here.
Even if this technique weren’t illegal, it still probably wouldn’t work. First of all, you’re going to run into trouble if you’re trying to count exactly 26 cards. Your wife is going to signal you while the dealer is in the middle of dealing the cards to everybody. Did she signal when the third player got his first card, or after the fourth player got his? What if the 26th card is the dealer’s hole card? You can’t count that until the end of the round, but you’ll have to start a new count for the next 26 cards before that, then go back and add the hole card to the previous count. You’ll also have to count the cards individually as they are deals instead of counting them in pairs or canceling the whole table at once. That is going to be more difficult and a lot more obvious to everyone else at the table. You are going to look like a rookie card counter. I wouldn’t be surprised if you miss a lot of signals because your eyes are darting all over the table during each round instead of watching for your wife’s signal. And even if you do manage to get the count for exactly every 26-card segment, do you think the dealer is going to grab exactly 26 cards every time? No way. There’s really no reason to make such an effort to count exactly 26 cards. It’s only going to cause more mistakes. Just use visual estimation. As ETFan said, if your estimation skills aren’t better than ¼ deck then you aren’t ready to track shuffles.
Secondly, you really need to be at the table while you are shuffle tracking, not hiding in the bathroom. The whole point of shuffle tracking is to visually follow the cards as the dealer shuffles. If the dealer makes inconsistent grab sizes (which most do) then you need to account for that in your formula. If the relief dealer breaks the discards differently than the regular dealer then you will be tracking the wrong cards and your formula will be completely wrong. Even a slight change in the location of the cutoff plugs or your deck estimation can render shuffle tracking useless. Arnold warns about this kind of blind map-tracking in his cookbook. He also covers simplifications that you can use and practice drills that you will need to master before you can even think about shuffle tracking. Reading that book will save you a lot of time, mistakes and money.
And what if you don’t get back to the table in time to see the cut? Then you’ve done all that work for nothing. Also, since you won’t be able to cut the cards yourself you will have to rely on a random cut from a stranger that will often not be helpful. These are all issues that will become apparent once you start practicing at home. The more you practice, the fewer questions you will have.
-Sonny-