When Jeph plans his guest strips he goes to his friends. You'll see a bunch of Topatoco people and maybe Danielle Corsetto; basically, his crew. The trick to get a guest strip going with him, actually almost anyone, is to do the best strip you can possible muster and then watch his/her blog and schedule. Send it at a time you think they are going to be busy in the near future and then just hope they use it.
It won't always work. But sometimes it does.
To my knowledge though Jeph did not publicly solicit strips for this week nor has he ever.
