Would think it unlikely you will be able to get the paint to 'key' into the plated surface without professional assistance? cheaper to buy a new end can, I have just picked up a titanium / carbon one brand new for £220 from fleabay
Depends what your after. You can get some matte black high temp paint (slightly grey once dry) and spray it, but it will never look like it left the factory like that. Good thing is, if you scratch it you just respray the scratched bit!