one of the things I have noticed only a few times when I simply start adding the new chords is that the melody and solo tracks can tend follow the scale of the original key. This results in notes in the melody or solo that can be "out of tune" with the song in the modulated key. It doesn't seem to affect the chords themselves but it can affect the notes played by the solo instrument tracks. Not in every place, but the occasional outlier.

For me, this is not a big deal. I can either edit it out or use melodyne to shift it half a step to put it in tune with the chord and new key.

You can find my music at:
www.herbhartley.com
Add nothing that adds nothing to the music.
You can make excuses or you can make progress but not both.

The magic you are looking for is in the work you are avoiding.