Dumb question???
What is the difference between using the pause and just waiting a long time to press the next space bar?
How many measures without lyric would
be the appropriate time for a pause??

Valid question! Instead of thinking "pause", think of it as a "stop sweep" operation. When you use CTRL, it causes the sweeping color go faster through the word, then stop (at the point where you tap CTRL). The sweep is stopped until the next spacebar tap to start sweeping the next word.

If you just use spacebar only, the sweeping bar will progress very slowly through the word you would/should have paused it on. By stopping the sweep, the singer is prompted to stop sinning. If the sweep is continuing slowly up to the next word, they are led to try to "hold" the word beyond where it should stop. This depends on the words within the song.

As to how many measures to hold, that also depends entirely on the song. In songs where there is a long instrumental pause, our Karaoke Pro commercial clients can even add a grapic image to appear while the singer is to be silent. Where there is a brief pause where the singing should stop, the singer will be able to take a breath if you stop the sweep.