Well this is
BA's restricted items list
The following list covers all those items that are forbidden to be carried anywhere on British Airways flights:
* Disabling devices - mace, pepper spray, etc.
* Security-type attaché cases containing dangerous goods - pyrotechnic devices, etc.
* Strike anywhere matches
* Cooking oils
* Flammable gas cylinders
* Flammable liquids - paint, petrol, lighter refills, solvents, varnish, etc.
* Flammable solids - firelighters, etc.
* Substances liable to spontaneous combustion
* Substances that emit flammable gases in contact with water
* Oxidising materials - paint stripper, etc.
* Organic peroxides - bleach, etc.
* Toxic substances - weedkiller, insecticides, etc.
I think you may be on a hiding to nothing trying to get a tin of paint on. Never mind the interest it will likely arouse when your baggage is found to contyain a sealed metal container with an unidentified liquid inside it.
Can it be FedExed or similar - and if not, ask yourself why you would want to fly with it if THEY won't ship it!