First, let me say you are a lucky dawg!!! That is one of the best smokers out there in my opinion!
wash all the grills and bowls with soapy warm water and rinse allow to dry. Double check all screws and bolts for tightness. Use a hose and thoroughly rinse out the inside of the smoker and allow it to air dry. Reassemble the smoker.
Take a can of non stick spray like pam or even olive oil in a spray can and liberally coat all surfaces of the smoker and the grates. You can cover the water bowl in a layer of foil to make for easier clean up.
Start some charcoal in a chimney starter and when ready, pour into your charcoal bowl And add a few pieces of chunk wood. Open up all vents as wide as they'll go and let it do it's thing. The smoke will begin to cover the insides and will help seal pores, prevent condensation and rust.
Once you can dump out the cold ashes safely, it is ready to smoke food in.
The manual from weber recommends a minimum of 30 minutes curing/seasoning for it's charcoal products to set the paint and enamels. A copy of the PDF manual is here http://www.weber.com/manuals/pdf_fil...620_080309.pdf