Here is the tressless' dude with amazing results :
Q: Did you start at 2.0 or work your way up gradually? If so, what did that timeline look like?
A: Started at 1.5mm but was at 2.0mm the next week. [The guy had hair so 2mm instead of 1.5?]
Q: It's hard for me to tell from the video, but are you slightly lifting each time after you press against your head, or are you keeping it at the same-level and just dragging it along like a lawnmower?
A: A mixture. Ideally it drags along but sometimes it sticks and you need to lift.
Q: How are you sterilizing cartridges and after how many uses do you switch them out?
A: I use a new needle each time now.
@pegasus2 to your point, changing needles each time sounds the right way to go.