1 to 2ml of FD20P dissolved in 500ml of lukewarm water in a hand sprayer, and as the wort comes to the boil give the foam a good spray as required to disperse it until a rolling boil is achieved.
I also do similar when transferring the wort to the FV with in-line aeration . . . It doesn't take a lot to bring the foam under control.
For my 18 Gallon FV a drop or two from a 1ml syringe into the FV sorts out any foam issues . . . even when I'm running wort at 2L per min and Oxygen at 6L per min