I've been treating my little critters to some rolled oats about once a week and some small applewood twigs every few days. Result! The girls let me pet them to my hearts content, even Annie who hates being touched (although she only lets me pet her while she's chewing. Once the bark is gone from the twig, I can sod off again!)
The biggest success has been with Buddy. He really seems to enjoy a good scratch behind the ear, just like his daddy did (although Hank would only let me pet him in the cage, Buddy has come up to me during playtime and stood beside my hand till I scratched him). He tilts his head and closes his eyes and stands up on his back legs. It really looks like "yeah, that's the spot"! He's also letting me groom him, as in pull the loose tufts of hair out of his hind quarters and in turn, he nibbles and fusses about my hand. I wonder does he think it's another chinchilla? Very cute!
It's so funny once he decides he's had enough cuddles though, after a minute or two, he starts hitting my fingers with his paw and pushing them away before running off to investigate something!