Painting white armour and black undersuit

Hi all,

I have spent the best part of a week trying to understand how to paint white armour for Empire units (mainly Scout Troopers) and have been unsuccessful at every turn. This is the same with the black undersuit too.

Is there any way for a beginner with painting white to get a respectable white amour that is not chalky, as we all as an underuit that doesn't look like flat black.

Any links to tutorials, advice or guidance is appreciated.

Cheers