Make a copy of your file under a new name to protect the original. Then try this…
Put the score into Edit > Concert Pitch if it is not already
Make sure all instruments are in the correct concert key-sig
Reduce the viewing size of the score (% pull-down in lower righthand corner)
Select the as much of a transposing instrument as possible
Use appropriate key-combo’s (see attachment) to transpose the music by octave, whole-step, or half-step into the correct concert key [Sorry, this is the most efficient means of group selection and transposing available in Dorico so far.]
Select further sections of the part until you have transposed the entire part.
Do the same for each transposing instrument until all instruments are in the correct concert key
Use Edit > Transposed Pitch to restore the transposed score and check your work.
I’d strongly recommend trying this out on just a few measures to verify that it works as planned with your import. doricoKeyCommands161116.zip (20.3 KB)
I would suggest adding new players holding new instruments with the appropriate transpositions, then ensure you’re in concert pitch (via the Edit menu), and copy and paste the music from the incorrect instrument to the correct one, then remove the incorrect instrument. Soon – hopefully even in 1.0.10 – you will be able to use a dedicated feature to exchange one instrument held by a player for another one, which will keep all the music but transfer it to the correct instrument.