As an example of how to paint the inner details, for the caged ball corner, I used a fine tipped brush that could fit through the bars of the cage and carefully painted the ball with a tiny amount of paint on the brush. this was a tedious process because I had to put the brush through each hole to paint the whole ball. In the process I did manage to get some paint on the bars. To fix that I just painted over it with the color that I was using for the bars.
The same approach applies to the other parts. Just do the innermost details first so that you can paint over any mistakes on neighboring parts.
Good luck with your painting!