This is an area of some debate. There are some that do not apply anything to the inside of drawers and those that do. If you have sanded the insides to at least 150 there really is no need to put any finish on as long as it is not for the kitchen or bathroom. Shellac is fine, one or two coats and knock it back with 320 paper. If you spray lacquer will work and once it is cured there is no odor.