you can buy stenner pumps pretty cheap.
https://www.amazon.com/Stenner-Pump-Company-QP255-1-Head-Single/dp/B00HEAPRKM/ref=sr_1_14?ie=UTF8&qid=1546180363&sr=8-14&keywords=stenner+pump+85mhp17
connect it to the liquid tank and time how long you have to press a button to dispense the necessary rinse agent.