Why wait? Use MicroPitch, H910 H949, or maybe HarModulator. Set up WET1 DRY 2 (or the reverse). DELAY(s) from 3 to 60 ms. PITCH(es) to taste. OUTPUT LEVEL as appropriate.
Yeah, actually Eventide designed the first doubler effect. It was even used in the riff on AC/DC’s “Back In Black”.
I would recommend you try the factory presets "BACKING VOCAL" and "FAT H910" in the H910/H949 algorithm.