To be clear, are you wanting to use the lyrics highlighting function (double-tap the left third of a lyrics line)? That works on a line-by-line basis, so I think it would be almost impossible to time that accurately without a backing track.
Have you tried using markers to jump between lyrics sections (verse, verse, chorus, etc)? That seems more useful without a backing track, because the timing wouldn't have to be so precise. You could start with an automation track, but if you needed to start jumping around manually, the lyrics would land in predictable places as opposed to using the plain scroll functions.
My other suggestion would be auto-scrolling, with foot switch buttons mapped to Scroll Document Up/Down, to make quick adjustments if the timing drifts.