I was reading elsewhere about how to go about removing the piston in my Lusso, and so I went about designing and making a tool to just that.
I measured my current PF, and ears, and basket, and so on, and then entered all that into 3d cad. I added a boss on the base of the PF to accept a 10mm diameter (bolt's post diameter) nut, plus a little tolerance to get it in and out.
The pictures are better than my words, so I'll shut up and upload....
The hex hole accepts the right nut size and holds it tight, with the help of a spot of glue.
The use of the tool is:
1 - remove the shower screen
2 - place something soft atop the bolt so as to not damage the piston face
3 - place the portafilter into the group, and then screw the bolt upwards until it binds on the piston.
4 - a little more force should allow the pin atop the handle assembly to be removed, then the bolt is relaxed and the piston lowers nicely.
I 3d printed mine in thick/solid abs plastic, and it fits like a glove, as it should. I have the cad files, I can post them somewhere if needed. I am not making these for you.