Here are the values for the Stucco Parametersrollout:
Size: 10; Thickness: 0.14; Threshold: 0.43.
You may experiment with those - the emission pattern will be heavily affected.
Column
width
60%
Image RemovedImage Added
...
Section
Column
width
40%
Select one of the Phoenix Sources and Left-Mouse-Button drag from the Stucco output to the Outgoing Velocity Mask parameter.
This will set up the Stucco to work as an emission modulator - black values will emit no liquid, white values will emit with full Outgoing Velocity.
Make sure to choose the Instance setting (as the Copy option will create a copy of this map - you want to use the same texture for both sources instead of being forced to deal with 2 separate Stuccos).