Good advice, although the answers did leave out one detail: Make sure that the keyswitches are triggered slightly before the first note to be played with the ks patch. If you have the trigger and the note occuring at the same time on playback, the ks won't work.
Originally Posted by rpearl
If you try everything else and the keyswitches are still giving you trouble, you can simply insert a note for the appropriate ks trigger in the instrument's staff. Here's an example from a symphony I'm composing:
In the above, the ks trigger note is changing the KS Violin II staff to the short bow (alternating up/downbow) patch. Should you go with this method, bear in mind that GPO remembers the last ks trigger used. If, for example, I wanted to change the KS violin patch to pizzicato later on, I would have to make sure and put in the correct ks trigger note right before the pizz. passage.
I recently upgraded to GPO4 and Finale 2010, but I haven't had a chance to road-test them together yet, so I don't yet know how well they integrate on the expression side. However, based on my experience with GPO2, I can tell you that the notation method for keyswitching is pretty much sure-fire.
Hope this helps!