Any electroplating demands "Pickling" before the plating process can begin. Usually Muratic Acid (Hydrochloric), to remove surface corrosion.
Can the treatment facility not offer shrink wrapping in plastic?
Otherwise, simply cocoon the shell in builder's quality polythene sheeting before starting the journey.
Personally, I wouldn't consider the electro-treatment before you sort out the body: any such material would create included slag problems when subsequently you start welding. Also remember, Jag joints are solder loaded: essential if you want the correct finish and durability. To properly tin the base metal then you would have to remove the electro treatment.
Which leads on to another interesting point: what would happen in the various dips, to the lead, if you elected to complete all necessary panel work and then have the electro process completed?
Might be worth checking with the contractors....