I want to tenderize conch meat with baking soda for the first time. It works on meats, beef, pork and chicken, but I have never tried it on conch meat. I have in the past, tenderized conch by pounding it and cooking for long periods.
While you might get a tiny bit of tenderizing from a baking soda soak, it won't do much to transform the physical structures that make conch tough. Mechanical tenderizing is the way to go - together with (typically) a very long and slow cooking time, or possibly cooking with a pressure cooker.
If you decide you want to try a baking soda "brine" I would recommend soaking briefly AFTER you pound the conch and making sure to wash the conch thoroughly afterwards to make sure you don't retain a soapy taste of baking soda that would ruin the subtle flavor of conch.
If you are interested in a chemical tenderizer for conch, you might consider some form of acid-based marinade - although, again, a marinade is going to transform the delicate flavors that characterize conch.
Basically, if you want to enjoy the conch-y taste of conch, I would go for tenderizing with a mallet and judicious cooking only.
You can try to tenderize the conch meat with a hammer as you are cleaning it, and put it on slow cook using a pressure cooker. Do not open it until all water is dry. Put enough water in, don't put salt at all and use bitter orange for the cleaning instead of lemon. Spice it with garlic and hot pepper in the cooking water. I'm from Haiti - trust me, I know how to cook conch.