Hi mate,
Here's three photos showing the stages I went through for my weathering:
1 - Paint with 'original' colours:

I just used the base colours I thought would look good. I painted after fully assembling the kit. Had I my time again I'd definitely try to paint as least some parts before assembly. I guess post-apocalypse is a lot more forgiving as mistakes can be hidden under weathering.
2 - Washes and inks:

After the 'original' coat was done I used a variety of thinned washes and inks to try to bring out the detail I was after. Stuff like the mortar work with the brinks and suchlike. I used mainly browns and blacks but got a pretty good result from grey in for the pink tiles.
3 - Drybrushing, highlights, weathering power and extra touches:

I used drybrushing with varying degrees of care (and success) to vary the colour and give it a more 'washed out' look. I also tried to apply some rust effects to the metal siding at the bottom of the model and on the stand-alone sign. I then splashed about some weathering power I picked up cheap at a local convention. I'd never used the stuff before and found the lighter colours just didn't show through. The real winner, for mine, was the violet. After that I glued on some tufts, static grass and model railway grass to make it look neglected.
More photos can be seen on this thread:
http://leadadventureforum.com/index.php?topic=104349.0I hope this is helpful
Happy to expand further or post soem photos of the interior if that'd help.