There are a lot of different coatings used to seal (undercoat) and topcoat wood baits. It's a matter of how complicated and expensive you want to make it. One of the simplest regimens I can think of is to finger coat the raw balsa with some liquid superglue to stiffen and strengthen the wood surface, apply a coat of D2T to waterproof the surface, lightly sand, paint, then apply a coat of D2T as a topcoat. That minimizes the number of coatings you need to acquire and yields a pretty durable bait. There are many liquid epoxies on the market. D2T is a popular choice but other slow cure (aka 30 minute epoxies), either designed for glues or decoupage crafts will work. Each has its peculiarities, good points, bad points, etc. They all usually require rotation for an hour or two after application to promote leveling and avoid drips and sags. It's also a matter of how patient you can be when making a bait. There are optional coatings you can use like uv cured polyurethane resins (Solarez, AlumiUV) that cure in a few minutes, moisture cured urethane that you can dip and hang up to dry/cure (KBS Diamond Coat, Dick Nite S81),etc. You need to read up on the options to choose what is best for you and the way you make lures.