The tubes are 2ft-long sections of 4in clear sch40 PVC pipe with an internal piston mechanism which pushes ~1.5gal of material out in ~1s. It's basically a scaled-up pneumatic potato cannon design, but operating at relatively very low pressure (~20PSI).
For manually-fired use like this, I've 3D-printed flat nozzles to screw on to the end so that the spray gets concentrated in a vertical line at the target. For overhead use, a 90-degree elbow is used.
I also have an attachment designed for injecting the front and back of a diaper (or other undergarment), for which I use a narrower pressure line to restrict the airflow so that it ejects slowly over 2s.
Love you, too
