Damn, I hope no one in the thread link above is in any way involved in engineering or maintenance.
The problem-solving skills - WTF? rigging tubes, pipettes, wooden dowels with paint or sharpie marker writing on it and the “I’m going to accidentally drop it in the tank”.
How about a simple aluminium (yes spelled/pronounced in proper Queen’s English) bar approximately 5mm thick and 25mm wide with the increments “stamped” into the metal. The top is either shaped into a “T” or “triangle” handle about 8cm wide. You dip it into the tank up to the handle (it can’t fall in, is clean and always measures to the same point).
I don’t know where these come from, but nearly every R44 I’ve flown in Europe has one similar. I’ve never seen the same in the US.