50/50 water vinegar for an hour or two till the rust is gone. be sure to wash with dish soap and hot water after. then toss it in the oven at 200 to fully dry then start your seasoning process.
as for lodge CI bluesman, if you have a lot of black gunky residue after a cook soemtimes you need more then just hot water. take a lightly oiled paper towel and some kosher salt and lightly scrub your greasy areas (not too hard). then coat rinse, dry on the burner, and coat with a thin layer of oil.
--Modified ECB---Mini WSM---22.5" Weber blue OTG---'69 18.5" Weber redhead----Mav ET-732