Tattooing is not difficult, you can do it with a needle and a pen. You simply need ink, and something sharp to drive it under the skin. Maori use a chisel tattooing technique, "hammering" an ink chisel into the skin. See video here: https://teara.govt.nz/en/video/41239/chisel-tattooing

The modern tattoo gun does this automatically by driving the needle in and out of the skin, so no need to hammer it down, but it's still going in and out of the dermal layer.

As for ink, soot was very common and easy to make.