I've also publicly given Hebrew names to several adults who never had one. I did this in the Friday evening service before the bar or bat mitzvah of a child or grandchild. They came up to do candle blessings as we traditionally do, and then we expanded that with a brief naming ceremony. In each case I present them with a certificate, the generic naming certificate from A.R.E. [a publisher of books and materials], offer them the priestly benediction and like to include their family in some way. I've had their children put their hands on their head for the benediction and given them some appropriate honor during the service.