Can one successfully split hydrangea bushes?

Yes you can - perhaps this video will help - https://www.youtube.com/watch?v=f421mSSukMA

Hi Dia,

I took a section of this website to answer your question. There is more information there about hydrangeas, if you're interested.

"Dividing Your Hydrangeas

When your hydrangeas begin to outgrow their garden space, consider dividing or splitting the plant. Separate the bush in equal halves by pushing the two sections apart to reveal the root ball or crown. Forcibly separate the sections using a shovel. Gently remove one section while keeping as much of the root structure intact as possible. Fill in around the parent plant's root structure with fresh topsoil and water daily until you see new growth, then water as usual."

From: http://homeguides.sfgate.com/caring-splitting-hydrangea-32210.html

Wishing you the best.