Ed, if you're going to spray lacquer, there's really no need for the shellac as a sealer. You can color lacquer with Transtint and many are self sealing, meaning they are their own basecoat/sanding sealer. Shellac has it's unique place in the finishing world, but lacquer sanding sealer would be as good or better in this case.
Years ago nitrocellulose lacquer was everywhere, then came catalyzed variants, precatalyzed (pre-cat) probably being the most common. Generally, catalyzed finishes add some durability, but film buildup needs to be monitored unlike nitro, which you can lay down coat after coat without worry for the most part. Before urethanes, polyesters and the like, lacquers were the workhorses of industry and can still be worked to an incredible finish via cutting and buffing. Get a run or sag? Sand it flat and recoat. Unlike polyurethanes and varnishes, lacquer slightly melts into previous coats which makes it very forgiving. The reason it's not as popular has mostly to do with the solvents and availability.
If you've ever sprayed Deft from a spray can, that's nitro lacquer. What brands do you have access too?