I try to draw a bg in my manga last week but in the end it's failed...
The master of clutter is Geoff Darrow. Both of those guys you mentioned are influenced by Darrow's work. Check out Hard-Boiled.
Not sure if anyone here uses Manga Studio but the perspective tools in that program are awesome and make doing 1, 2, and 3 point perspective backgrounds really easy.
Some neat tricks and tips in here!
But no remedy to solving my laziness when it comes to backgrounds. /sniff D':
Its really good to me and at least you tried. I got lazy, I just draw a rough out line of my backgrounds and finish them in Photoshop.