Synchronizing moves requieres a lot of practice and understaing each other... The girls who do synchronized swimming, for example, need to be all the day long training in the water in order to achieve symmetrical and synched-up movements... There are different tricks that may help you, like tying the hands, something that holds your leg next to your partner's, the rhythm of a song or sharing a dildo...
ExtraBall by walter
Dressed up as Launch, that girl from Dragon Ball who switches between two different personalities each time she sneezes.