You should always wash your plastic or resin bits in dishwashing detergent before priming and painting.
The bits are usually coated in a "release" oil that helps to get them out of the mold. This oil will cause your primer/paint to have trouble sticking to the bits.
Live and learn thru spazzed out excitement!
The 'Rust Paint' formula/instructions can be found here...http://www.wideopenwest.com/~tinweasel/rust_tut.html
Less than 24 hours and I can see rust starting to form!