A single delay:

chorus=0.7:0.9:55:0.4:0.25:2

Two delays:

chorus=0.6:0.9:50|60:0.4|0.32:0.25|0.4:2|1.3

Fuller sounding chorus with three delays:

chorus=0.5:0.9:50|60|40:0.4|0.32|0.3:0.25|0.4|0.3:2|2.3|1.3