I exported a Finale file to MUsicXML but I apparently have to somehow update the file to allow the assigned instruments per voice to load.
Additional complication - althought the voices are nominally SATB, I like to assign other instruments (e.g., strings, horns) to get the effect I want. I’m thinking I need to save the file as a dorico file first in order to assign instruments to the voices, but I’ve been busy with other projects. Any advice?
I’m not quite sure what you mean. Is the issue that after opening your MusicXML file in Dorico, it doesn’t play back as you expect? If so, try re-applying the factory playback template in Play > Playback Template.
As for how to change the sounds used in playback, please see this video: