Chinchillin is a form of extreme chillin. Usually performed after a lame ass day of school and/or work. Alcohol, weed, ecstasy or cocaine must be used before attempting to chinchill.
A higher level of chillin' or could be a reference to comfortability around chinchillas
I'm chinchillin' with a chilly chinchilla just chinchilln' on my chinny chin chin chinchillin' at a chilly Chili's chewing on chilled chinchilla (who also has a chilly chinchilla...)