Here’s another interesting bit from Harpokration’s Lexicon of the Ten Orators:

§ a193 Apomatton (wiping off): Demosthenes in For Ktesiphon. Some understand it plainly for ‘wiping away’ and ‘cleaning oneself,’ but others more elaborately, as ‘plastering clay and bran on those being initiated,’ as we say ‘to wipe the statue with clay’: for they used to anoint with clay and bran the initiates, imitating the stories told in myths according to some, that the Titans hurt Dionysos by plastering themselves with gypsum to avoid being recognized. They say that then this custom has ceased, but that later people smeared themselves with mud for tradition’s sake. Sophocles in Aichmalotides: ‘purifier of the army and experienced in rites of cleaning’ and again: ‘and most skilled wiper-off of great misfortunes.’