Welcome to SMF bestway, Glad you're here. If you wish to brine the cornish hens, consider approximately 4 hrs. There are chicken brine recipes all over.
If you haven't signed up yet, consider Jeff's 5-day eCourse to help you along with smoking (located in the upper left of the page in highlight)
Don't forget to check in at the roll call area to introduce yourself and get a proper hello. What smoker are you using? Feel free to stop into the chat area or post any questions you have. There are lots of helpful people here.