Ball rasp in the drill press for the cupped mouth. For screw eyes, get stainless steel ones. The longest ones that will fit the plug without going through the other side. Probably want to tail weight them for casting distance.
Well having made 1 or 2 blue fish popper in my time.... I'd say even weight on the bottom 1/3 and 2/3 with center hook. or use very hard wood like I do and avoid the weight. for the cup I round off a 7/8 spade bit on a grinder and use that on high speed on the drill press. If you get a bit I'll grind it for you. It's a standing offer with anyone out there just send me an email and you can come by I'll grind and test it for you. armandt@atlanticoffshorelures.com