One thing I find about correcting timing is that you can often be led down the wrong path, for example you might think a note is out of time but it can actually be the previous note(s) that are wrong. Worth looking, tweaking and listening before and after the bit that sounds odd. Say someone is rushing into the chorus and that makes the chorus sound slowed down but in fact it’s the rush that needs correcting.
Another idea would be to double track a section, this can disguise the discrepancies. A quick way of double tracking is to dup/cut/paste the same track but different bars, e.g. swap two choruses in the song (only works it recorded to a steady tempo of course!).
Finally, once you’ve started to time up some instruments it will usually reveal problems in others. I proceed methodically through the tracks: drums, bass, guitar, keys, vocals, BVs, whatever, and it takes time. I use the screen to do things quickly but I always use my ears to review the result.
Mike.