kistky and wax
Kistky (s. kistka) are the tools used to "write" on the eggs with wax.
1.) Used block of beeswax for traditional and delrin kistky.
2.) Traditional kistka
3.) Electric kistka
4.) String wax for electric kistky.
(Both of the wax samples seen here have a bit of black dye in them - if you don't use the traditional tools and hold the wax in a candle flame (thus exposing it to soot), it isn't very visible on the eggshell. Dye solves that.