Here's a link to a Finale 2005 file which has the keyswitch information programmed into text expressions. No more extra staves or hiding notes.
Following Robert Piechaud's instructions, I've programmed all KS information for the strings, woodwinds and brass instruments. These expressions can be placed as either note or measure expressions. They work instantly on the note they are attached to. There's no need to place the expression before the note.
For the strings, there are multiple sets of expressions because the KS keys are different. The string KS expressions also work for the solo string instruments. The exception being the playable tremolo and trills which use release triggers. The keyswitch actually does trigger the correct key, but you still need to input repeated keystrikes to make it work. There is a restrike midi command in Finale, which uses executable shapes. If there's a brave soul out there who wants to attempt that, be my guest.
All of the trills use the standard trill symbol and will look normal on the page. Just be sure you attach the correct expression.
Similiarly in the woodwinds and brass keyswitches, there are multiple "mute" expressions for example. Each for a different group of instruments.
Each expression has a description line which tells you what instrument the expression is programmed for.