When I studied conducting at the conservatory, we always had, well, scores to work with. I got very good at reading, understanding, and working with full scores for many sorts of ensembles. And when I work with a band, orchestra, or chorus, these skills still serve me quite well.
The ways that I have historically prepped a score primarily involves taking the time to go through each part, and mentally re-building them on top of each other until I can hear every part clearly, and then I make my nuanced decisions and my rough plan of attack for the rehearsals themselves. By the time I arrive at my first rehearsal, I am prepped and ready to go.
However, lately, I've been getting gigs in the realm of musical theater, and the so-called "conductor's scores" are really just piano reductions with cues indicated (ie.
w.w. for "wood-winds", etc). While I can get the tune, the rhythms, and the harmonic motion from this information, I can't construct the sort of mental model that I usually depend on, and my rehearsals have involved a fair amount of nonsense like "wait, you have that written in your part? Well, then what do you have in this other measure?"
This is not a good way to run a rehearsal, but I am missing a lot of data. However, I know that there are many MDs who work with these kinds of scores for a living. Do any conductors out there have tips for how to prep for an efficient rehearsal with such a score? There are so few details, it is hard for me to know where to begin.