I'm given to understand there are multiple companies manufacturing those back massagers in different shapes and colors these days, if you need one that can reach into those tight places under the hood without relying on the PVC pipe to help it along.
As I understand it you can even source them with specific bend and taper profiles, which lets you optimize for the geometry of the system you're trying to flush.
I've seen one recently that seemed to be long and skinny enough where if OP could see the part, he could vibrate the part. I have no idea what part of the human anatomy such a device is necessary for. Maybe top-of-the-foot while standing?
