I have been experimenting with jets, my jets are now on stalks, right on the glass, no bristles to get in the way and so simple.
I use Algarde 6mm silicon tubing.
1] drill two 5.5mm holes through the brush where you want the jets to go
2] thread the tubing through the holes
3] insert the jets into the end of the tubing
3] pull back the tubing until the jets are level with the top of the bristles.
£2 buys you a packet of micro watering system T pieces from B&Q, these have a 2mm bore.
Just cut them off where they join the body of the T, so you get three jets from each one, insert the piece you have cut off into the end of the Algarde tube, job done.
The bristles keep the stalks in place.