One way to get a feeling for a 2-beat kick is to stand and rotate your body about the axis of your spine while keeping your feet in the same position on the floor. The motion of your legs relative to your body when you do this is very similar to the motion they should be making relative to your core body rotation when you are doing a 2-beat kick in the water.
Another thing you can do, if you have access to water that is over your head, is to do vertical kicking while rotating your body about the axis of your spine, first in one direction and then in the other. If you can eliminate all kicks except the ones that are rotating your body, you will be doing a 2-beat kick.
One of the things people sometimes do that helps them get the feel of a 2-beat kick is to try to swim without kicking. It is virtually impossible to really do this (i.e., not kick), so they end up doing a 2-beat kick.