Sugru - not cheap, but simple & resilient.
(No affiliation, I just use it a lot for all sorts of things)
From Sugru's own web site - 8 ways sugru can refresh and improve well worn products
Rub a contrasting colour into the 'grain' of the markings & rub off the excess. Leave overnight to cure. Starts off like 'plasticine/silly putty' modelling clay - dries like rubberised plastic.
Amongst other uses, I've had some on chipped cups that I use every day & that go in the dishwasher all the time. Still sound after several years.
I just realised in the example they appear to be using some kind of wooden palette knife or spatula. I've found a thumb is quite sufficient; it's nowhere near as messy as the pic makes it out to be, thumb, finger, one piece of kitchen roll, done.