I'm no help as far as re-etching or re-painting, but just wanted to mention I'm using the same Pyrex measuring cups that I've had for decades and the measuring lines still look like new. They've seen the inside of a dishwasher countless times. I have a 4-cup, two 2-cups, and 2 one-cups.
I would go ahead and buy new, unless this particular measuring glass is of sentimental value to you. I can certainly understand that, I've got lots of kitchen tools that have that value for me that I'll never part with.