How you you clean your vintage model boxes?

Or do you clean them..........

I bought this .074 Ok Cub mostly because of the box.  The engine itself is trash but restorable.  It looks like someone glued it on a firewall after the radial mounting holes broke. Everything was bound up, back plate, needle valve,  piston and crank case.  A hot Simple Green soak loosened it up.  



This is a case where the previous owner took reasonable care of the box but mistreated the engine.  The box contained everything that came with the engine as pictured.  I used a paper towel soaked in warm water and a mild detergent to wipe the box and some of the contents, but I'm wondering if there is a better way?



Some of the coloring came off on the paper towel, but it did clean some of the dirt and discoloration off.  It came with a formed wire.  Some sort of a tool or perhaps a nose wheel strut?



I'm surprised to see that the selling hobby shop took the time to stamp the warrantee.