I think it does depend on whether 1 has taken ADs previously, as I never had to 'wait' to feel effects, good or bad. The latter struck within 24 hours ......... escitalopram suits me fine for now. One AD can't remember which: I took 9 weeks to wean off with GP supervision.
I also used Bachs Flower mouth spray with success, would use it 30 mins B4 an event and never wondered whether it worked/not. Never required an extra squirt ;-)