I believe that Ian W has used a Numatic trigger on at least one of his poles.
Is that right, Ian?
Maybe you could let us have pictures and the benefit of your learnings?
Yes, Wally. I use the Numatic trigger and it works well. Easily fitted on my pole using a velcro strap. This makes it easy to move up and down the pole and, using an Unger Teleplus, easy to move onto the extra sections if needed.
You can also save a massive amount of water by giving the window a quick spray of water, then scrub, then turn water back on to rinse.
I clean a massive house right by the sea and always covered in salt spray. It used to take about 200 litres of water without the trigger. With the trigger, it takes about 75 - 100 litres.
The trigger also comes with a big fan jet. I have this mounted on a brush as an overhead jet. Different technique to the usual jets, but works well.