Welcome home, hope you have a good summer break.
I spoke with the assurance of a person that was actually given training on using dye-pen
It is easy, if you can read the instructions in your language.
I was once asked to dye-pen a head. When I did so, the dye clearly showed a crack running parallel to the landing the across it and also between the valve ports. When I showed the old Chief, he looked at me, looked at the cracks and said, can you weld it? Ummmm, no.
Years later, after paying 25 k to purchase replacement heads, I now know where that question came from.