There are smart slot gamblers, they are those who can control themselves while playing it. The same as in most other gambling games, smart gamblers does exist although the number is low. As long as we know how to deal with all gambling situation wisely, we are smart already. Smart gamblers are not depending on what games they play, but more about how they play it in all related aspects such as emotion, money management, time management, etc.
No strategies work on slots, that's the thing, it's totally random, there's no pattern. The only strategy, if you can call it that, is your money management. It won't help you to win, but you can last longer, months instead of days, with a proper money management. During this time you can win big, it is not ruled out, but it's never guaranteed.
It's important to understand that your mind set and the outcome of a slot spin are not related to each other. You can be greedy and still win a huge amount, or, you can be calm as Buddha and lose everything. Just stop when you've lost 10% beyond what you can easily afford to lose. There are no "smart gamblers" who know more than that.