Can I use Powerball in both hands?

Absolutely! Powerball is designed to spin in a clockwise or anticlockwise direction in either the left or right hand and this can be altered while the rotor is stationary or spinning – the only caveat is that you don’t switch rotor spin direction violently! (oh it will switch between a clockwise and anticlockwise spin in the blinking of an eye but doing so at high speeds can cause undue wear and stress on the rotor support band and is therefore best avoided!).
 
Some experienced Powerballers will also use two Powerballs simultaneously which is an incredible way to train and improve your co-ordination!

If you can already use one Powerball in either hand then two is a piece of cake - you'll most likely be a little perplexed as to how to start them both but after a little while you'll be the master.

When you're using one Powerball it's fairly easy to keep it going indefinitely if you're alternating hands (one hand will always be resting)... but with two Powerballs you immediately forfeit that option - Wrist Straps would be a good idea.

Remember to avoid letting your Powerball rotor spin-down or decelerate freely (sometimes it makes a rattling noise as it does), you need to keep a 'resistive' grip on it to let it wind-down properly. With two balls, either hang your arms by your side, or clamp your hands between your knees, or place your hands on a surface with the Powerballs facing up or away from anything being able to touch the surface of the spinning rotors. Always keep a firm grip on the ball, you will feel it pulling, getting slower and weaker as the rotor decelerates.