I am breeding every year and never had the need to use hormones. When a sharp rise of temperature is expected the next day, I put two males and a female in the spawning tank filled with fresh water to about 40cm, add a good supply of oxygen, add spawning material, and nine out of ten times, they spawn the following morning or at least the morning thereafter.
Provided of course that you had at least five consequative days with at least 21 degrees C.
If you want to spawn in the pond, do a good waterchange a day before a rise in temperature is expected, lower the water level to create a rise in water temperature, add spawning material, and the chanches are good that they will spawn the next day, especially if it rained the previous day.
Don't under estimate the power of the full moon. The Japs believe in it, so I do. They have all the experience.