We hear you, and we've got a solution you may not have considered. It's the old-fashioned, hand-crank egg beater from dorm-room days or grandma's kitchen. Also known as a rotary beater, this simple, no-frills device was once standard equipment for home chefs, and it got the job done - with no electricity, just lots of wrist action.
When using a Boston shaker, a bartender must master the proper sealing angle, a secure hold to avoid spills, and ultimately the technique to separate the two components once shaking is complete.