Gradual changes of dynamics are significantly more difficult to show than sudden ones. The simplest way is to increase or decrease the size of your beat gradually. Once comfortable with that you can increase its effectiveness by involving your left hand: raising your left arm with your palm upward, and lowering it with the palm downward. Meanwhile your right hand continues to show the beat pattern which also increases or decreases in size. This will require a good level of hand independence and may take some time to become automatic.
In the following exercises be careful to maintain a steady pulse. Using a metronome will help.

Exercise 1
First, set a metronome to a comfortable tempo such as 72bpm. With your right arm at rest by your side, practise raising your left hand (palm upwards) for 4 beats and then lowering it (palm downwards) for 4 beats. Make sure the movement is smooth. Try to feel as though you are lifting something when raising your hand, i.e. as though lifting against some resistance. You need to focus on the steadiness of motion.