Painted enclosures - faraday cage?

[jwin615]

I am still a bit curious about the original question about a Farady's cage here. Is an enclosure without a lid still 75% such a cage? Or is it "all or nothing", eg. better ground the lid with the rest of the enclosure?

No. That would be a faraday hat.
Everything needs to go to ground.
Cracks are way worse than holes. Any crack will allow rfi passage of a frequency with a wavelength 4x it's length. i.e., 1 Ghz is 30 cm, so it and any frequency at or below 1 Ghz could pass through a crack of 7.5cm.
If the material is ungrounded, the RFI will only be attenuated.