Good point.
I have been playing bits and pieces of Rush for almost 30 years. I don't know an entire song as I don't really gig Rush tunes, but once you play a bunch of different Rush songs/riffs, Geddy is pretty easy to figure out. Lots of root/octave stuff and he likes a few similar patterns. He can play fast, but it isn't nearly as fast/complicated as many of Jaco's lines.
My point is, practice the song until you get it right but be conscious of what you are playing and where. Geddy also sings and plays a ton. He doesn't tend to fly all over the neck when he is singing.