Not a problem, but might I suggest you use a lighter shade of blue. Using Midnight Blue over Chaos Black is going to make this model perhaps abit too dark. I suggest using Regal Blue instead, with a lighter blue as a highlight.
Here's a kindof step by step assuming you are using a model from the Cadian box.
1.) Spraypaint your batch of models (I find it best to paint half a squad at a time, 5 models generally). Give them enough time to dry, I am usually painting something else so I leave mine for around an hour or so...but they don't need so long really.
2.) Once they are dry paint any fatigues Regal Blue, take care to leave small shadows in the recesses to simulate depth. (Alternatively you can paint them midnight blue, then paint regal blue over that...just a thought). Do not paint any skin, armor or the boots in this way, you just want the cloth to be blue.
3.) Paint the armor again with black. Yes, I do know you just spraypainted the whole model but you should be sure all the areas are covered. You might have missed some when you sprayed, or they are not covered well enough to be considered a "black surface". Do the same with the helmet and the boots.
4.) Paint the skin with Dwarf Flesh, like with the fatigues leave small shadows in the recesses and creases of the face, but don't leave thick lines, leave a hint of black.
5.) Highlight the fatigues with a lighter blue like Lightning Blue or even Hawk Turqoise.
6.) Highlight the armor with Fortress- or Codex Grey.
7.) Paint the face with Elf Flesh, covering the dwarf flesh with a thin layer of Elf Flesh and highlighting the rest.
8.) It's up to you to paint any other stuff such as grenades, pouches and the lasrifle. But I'd suggest painting the pouches in the same way as the fatigues and since you have such a dark color scheme I'd suggest something like a black lasrifle. There are various guides how to paint eyes out there so find one you like. I'd suggest painting Aquillas silver or gold, goes good with the dark color scheme.
To save yourself heaps of time paint all the models in each stage. So, do the fatigues on each one, the armor on each one etc. until each model is done. This way you finish off loads of models at once instead of doing each one from start to finish.
Any questions feel free to direct them to me.
Also, check out my guide to painting Urban IG which can be found
here.
And the Cadian model addendum that can be found
here
Hope it helps!