toggle servo movement (CCW and then CW) with momentary push button switch.

switch_spray.ino

#include <Servo.h> 
 
Servo myservo;

int servoPin = 9;
int switchPin = 2;

void setup() 
{ 
  myservo.attach(servoPin); 
  pinMode(switchPin, INPUT);
  pinMode(13, OUTPUT);
  //Serial.begin(9600);
}
 
void loop() 
{
  int switchState = digitalRead(switchPin);
  //Serial.print(switchState);
  if (switchState == HIGH) {
    digitalWrite(13, HIGH);
    spray();
  }
  else {
   digitalWrite(13, LOW); 
  }
}

void spray()
{
  int pos;
  for(pos = 0; pos <= 180; pos += 1)
  { 
    myservo.write(pos);
    delay(8); 
  } 
  myservo.write(90);
  delay(10);
}