Any effect that will sustain the note longer (distortion, compression) will help you hear the beating effect.

Harmonics are a great way to tune because you can have your fretting hand free to turn the tuning pegs and you are not putting and extra tension on the strings by pressing down on them. Couple this with distortion and the notes will sustain long enough for you to tuen in one hit.

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Remember, If it was meant to be easy everybody would be a great guitarist.