The highlights on that tank are neat, I like em. You should try hitting up those metallic areas with a Badab Black wash though - they're really bright right now, and very flat looking.
My next step for detailing the tank would be to wash in the recesses. Take a moderately thin brush, and go into the crevaces and armor joins and just do thin lines of Badab Black or whatever suits your fancy. Finally, I'd weather it - just a drybrush will do the trick. It seems really scary at first, but you'll find it's great fun to mess up your paintjobs!
Just as proof in case you're not sold on the idea yet, I did that same Badab Black wash in the recesses + drybrushes of Graveyard Earth and Kommando Khaki on a somewhat darker blue tank, and got these results: