Good luck with the bust, it's a neat one! You could try mixing in some grey with your green highlights to desaturate them. A dark blue or purple would also make some nice shadows for the green. I'll be keeping an eye on this project.
ArchArad, my general rule of thumb is glue together as much as you can before painting but, if something is going to be hard to paint around or just really fragile, I'll leave it off until later. Before I leave a part off I'll dry fit it first to make sure there are no issues. If there are gaps that need to be filled, seriously consider whether you really need to paint it separately because that is definitely a pain! Another tip, I've found that sometimes the superglue fumes will leave a white film on the figure, screwing up sections I've already painted. You can avoid this by not using too much glue and placing the mini in front of a fan while the glue drys.