Disguising topspin serve

I have been trying to disguise my topspin serve but i just do not get the hang of it what can i do to disguise my topspin serve

Hi,

For the Pendulum serve hit the ball a little later in the swing when the bat is starting to go upwards.  This will mean that you will brush the ball with topspin.  The closer you can get the contact to the end of the downswing and the start of the upswing the harder it will be for your opponent to tell what type of spin you are putting on the ball.