My ink recipe that seems to work well....
Some rust-oleum paint (colors vary)
Paint thinner
Dot 3 brake fluid
Depending on how thick or drippy you want your tag
Pour paint into a thick plastic container(This with the Paint thinner will eat away the side and come out everywhere)
Pour your paint thinner into the container(more or less depending on if you want drippy or thick)
A little bit of dot 3 (it goes a long way, Leaves a ghost tag when buffed)
And a marble if you want to mix up the paint inside....That seemed to work for me and my kiwi mop
Enjoy!