Control speed of linear actuator servo
Have you tried something like the following?

#define STEP 50

void loop() 
{ 

  // if the pushbutton is pressed set the linear value
  button1State = digitalRead(button1Pin);
  if (button1State == HIGH) {    
    // set the position value  
    if (linearValue &gt; 1050)
       linearValue = max(linearValue-STEP,1050) ; 

  } 

    if (button1State == LOW) {    
    // set the position value  
    if (linearValue &lt; 2000) 
       linearValue = min(linearValue+50,2000) ;  
  } 

  //use the writeMicroseconds to set the actuator to the new position
  LINEARACTUATOR.writeMicroseconds(linearValue); 
  delay(100);  
} 


By changing the STEP value (or the delay in the next-to-last line) you can change the speed of the servo.