Actually, smoking is usually not done to meat unless it's cured first — I assume you mean real smoking, not cooking in a barbecue with some wood chips for smoke. The brine used for curing contains salt as a minimum, which does preserve the meat. I also use sugar and sodium nitrate in my cure. this provides the preservation, the smoking provides more flavor.
To really preserve the meat you'll need to cure and smoke the meat until its fairly dry. The salt draws out the moisture from the meat. In this case, starting with dry salt is usually the procedure.
And you don't necessarily have to freeze the seared meat, just chill it very well. Do you mean for something like a carpaccio, but with a cooked crust? The searing helps to firm up outside of the meat, and then chilling it firms up the inside. Would you be hand slicing, or using a mechanical slicer? In any case, if you DO freeze meat to make slicing easier, you don't really want to freeze it solid; just enough so that it's not squishy.
As bouland said, most meats that are smoked are cured first. This is usually done with a salt and sugar mixture though it is possible to cure with salt alone, and even sugar has some curing properties. Sodium nitrate also helps the preserving process in that it helps to keep red meats looking red. It is difficult to find nowadays, in the US (for the consumer) as the FDA has really clamped down on its use. I know the Spice House, in Chicago, carries a curing salt that contains trace amounts of Sodium nitrate.
As for smoking, alone it does have some preservative properties. Not only does smoking help to dry out the meat, smoke also does seem to contain some chemicals that help in the preserving process, but for the best way to preserve and for the tastiest meats a combination of curing and smoking is the way to go.
I haven't looked recently, but I have seen Morton salt cure in the grocery store. This particular brand has salt, sugar sodium nitrite, sodium nitrate and sodium erthyobate. The nitrite/nitrate mix is so that the meat doesn't grow botulism during thre smoking process since smoking will not necessarily cook the meat above 160F for long enough to kill the botulin spores and with the smoke in there it is considered an anaeroblc environment. The erythobate and sometime soduim ascorbate are used as "helpers" to reduce the amount of nitrate and nitrite in the cure.
BTW- air drying and smoking meats are somewhat different in method.
Sidenote- I spent a couple of years making and smoking sausage at a restaurant where I worked. People would get upset because even though we make our own stuff it still contained nitrate and nitrites and that was shortly after the beer/nitrosomines scare. Most people have forgotten why chemicals are used. Where now, maybe if you consume enough cured meats, mix with enough other stuff (like beer), it MIGHT increase someones' risk of cancer. But before the use of these preservatives in meats, people died of botulism ALL THE TIME! Better living through chemistry!
It would not be neccessary to brine (or cure) the meat first since you really aren't attempting to preserve the meat, but curing and brining are ways to add other elements of flavor to the meat. Chiles, spices, onions, garlic, herbs, etc. can all be used in conjunction with the curing or brining process to add added levels of flavor, but in your case it is not absolutely neccessary.