So I added the delay plug-in after the reverb to add the effect. But that made the reverb too delay-y, so I turned the wet/dry signal to 50/50.
That way some of the reverb came through unaffected to add normal space, while some of the reverb was delayed to add a subtle echo effect.
After adding an EQ to filter out the highs and the lows, the vocal space sat nicely with the rest of the mix.
Thanks to Björgvin Benediktsson for the tip…