You put the stick in the powder to take the sacred ashes — well, they're not ashes, they're burnt limestone — to empower the coca leaf, to change the pH of the mouth to facilitate the absorption of cocaine hydrochloride.
Se pone la vara en el polvo para tomar las cenizas sagradas — bueno, no son cenizas, es piedra caliza quemada — que estimula a que la hoja de coca cambie el pH de la boca para facilitar la absorción de clorhidrato de cocaína.