to work on something with a chisel; to carve; or, for a painter to put gold leaf on something, to make it golden (see Molina)
Alonso de Molina:
teocuitla cuicuiloa. ni. (pret. oniteocuitlacuicuilo.) labrar algo de sinzel, o dorar algo el pintor o el dorador. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 100v. col. 1. Thanks to Joe Campbell for providing the transcription.