State of the union (And by union, I mean Chaos)

So, the Chaos Warhound Titan came in yesterday, and along with it was a Forgeworld Iron Warriors Dreadnaught with a Chaos Plasma Cannon and a Chaos Chain Fist.  Needless to say, I was happier than a pig in shit.  So, as I work on cleaning off all of the shit attached to the pieces of the Titan, I began wondering about how I am going to paint the pieces.  The conclusion I came to is that it will be in SEVERAL pieces, then green stuff so there are 0 gaps, then painted, then matte varnished, then glued together, then touched up, then matte varnished, then weeped over in tears of joy.  The other thing I will be trying is weathering powder.  Being from the dark side of the playground, and given the Nurgle theme of my army I am building to showcase with this bad boy, they shall be rust!!!  However, I have never worked with weathering powder, so I need help.  If anyone out there could tell me a good way of achieving rust effects using weathering powders without over doing it, I would be greatly appreciative.  I'm not weathering EVERY piece of metal, but there are some spots that are prime candidates for it, and on a piece of this size, I want it work out right.  So, any help would be much appreciated.  Also, I plan to get pics up of the pieces as I get them into the groups I will be painting them in, as well as the Death Guard termi's.  On order as well are some Blight Drones, some FW plague marine upgrades, and a Death Guard Dread.  Also on ebay, I purchased a Nurgle Dread and a Nurgle Chaos Marine Sorceror.  Should be fun.  Anyways, I'm off to the Doctor's and then I have some dremeling and sanding to do, so I bid you all a fair well.  And remember, HELP ME WEATHER!!!!!