Mass Mover Tool.
Mass Edit Menu - Utilities - Respell NotesThis command will respell the notes in the selected region according to your settings in the submenu
Options menu - Enharmonic Spelling
However, the responsibility still lies on your shoulders.
What region you select, is your choice.
And it is also your choice, what settings you pick in the submenu
Options menu - Enharmonic Spelling
Basically, Finale only does what you tell it to do. Finale will choose between G sharp and A flat according to your settings. But it is your responsibility that it is correct to spell all the notes in the selected region after the SAME rules. Be careful with, what region you select!
Peter