While a dedicated mixing glass and bar spoon are ideal for optimal chilling and minimal dilution, you can improvise. A tall glass (like a pint glass) and a long spoon will work. Just ensure your improvised mixing vessel is large enough for ice and ingredients, and your spoon reaches the bottom to stir effectively.

Yes, 15 minutes is realistic for the active mixing process. For beginners, the main time investment might be gathering all the specific spirits. The initial cost for quality gin, vodka, and Lillet Blanc can be an investment, but these bottles will last for many cocktails, making subsequent Vespers very cost-effective.

Lillet Blanc is crucial for a true Vesper and doesn't have a direct substitute that yields the same flavor profile; its absence changes the drink significantly. For orange bitters, while specific, you could omit them for a classic Vesper, but they add a lovely aromatic layer. Other aromatic bitters might alter the drink too much.

Stirring is preferred for spirit-forward cocktails like the Vesper to achieve a silky texture and clear appearance, as shaking can over-aerate and cloud the drink. To avoid over-dilution, use large, fresh ice cubes and stir for the recommended 15-20 seconds until well-chilled, then strain quickly.