Introductory Bars

I'm notating scores and exporting practice tracks for a choir. To improve the practice tracks, I want to add some intro bars that give the starting note and then count in, much like we're used to when actually at choir. This is for inclusion in an mp3 export, and has to come after the starting note, so the count-in feature for playback isn't what I need.

So far, my approach has been to give the starting note in each part, and then two bars of a drumset playing a simple part, and then the score proper starts.

I've got one issue that seems buggy, which is that "exclude from bar count" doesn't seem to work except for the very first bar.

And the other thing I wonder about is whether I can make those intro bars completely invisible to the score. I can make them invisible, but the space they occupy is still used up - just by blank space instead. Is there a way to disappear them completely?