undercarriage care question

Hello guys ... Can anyone recommend the best way to tackle the undercarriage. I recently purchased a 69 ss 350 camaro from south carolina
& I am very pleased with the car. I took the interior panels off and coated the rear quarters and inside of the doors with a product called " rust bullet ". The metal is all original & the floor pans as well as the trunk are in excellent condition. Other than a little flash rusting, the car is as rust free as they can get. The undercarriage was never undercoated & looks great. There is some very minor surface rust in a couple spots .... other than that, it has never been touched. I was originally going to coat everything with a rust inhibitor & coat it with a chassis black topcoat ( probably eastwood brand ) but, I have been thinking more about having a detail shop steam clean it & first. Does anyone know where I should search for someone that does this type of work ..... I don't think body shops would want to deal with this type of work ?? Or would Ziebart be an option for steam cleaning & preserving the undercarriage ??
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