Silver Sharpie for dark items, Black Sharpie for the rest. Copy the s/n of your regs and leave it somewhere safe yet accessible, in case of discrepancy.
Same here...
Also paint pen on Cylinders and hard weights. I also do the weight of the weight to make them easier to spot.
I initial to distinguish gear common with my wife. The major marking is my phone number with area code. If someone finds my stuff I want them to be able to contact me.
Re-coat annually.
Pete