Step 2: Patterns.
Make sure you have a sharp iron saw. When I first used a fairly blunt one, the roughness of the cut caused strange unwanted patterns.
In the picture you see three different notches I have tried:
will generate a sheet that has the shape of a pizza slice.
will point the sheet in a certain direction. Ideal for dead corners like flower beds.
Cross cut notches
will combine a bit of both.
Best is not to cut the notches very deep (you want a high pressure and low water consumption) because you can always cut deeper if it doesn't work at once. In this way you can gradually determine the depth of your notch.
I was surprised by the effect of one small notch. The notches in the first picture are definitely too deep.
Spacing. I have started with one cross notch because the area is not large. I figured if it didn't work, I could always cut some more.
If you think you have an alternative patterns that works, you can always test it on a small piece of copper tubing before you decide to make the final cut.