I know there's an appropriate place for this, but I can't find it on this clunky board.

When you're weathering a TARDIS, you need shadows and highlights. 

I've found the shadows to be (relatively) easy.  You get yourself a bottle of black paint and water it down.  Then you apply it with rags, spray bottles--whatever can make the appropriate dark bits. 

For me, the highlights have been trickier.  In theory, it is the same thing--you do a white/light blue, and hit the edges and corners and highlights with it.  Somehow it doesn't work as well as the shadows (for me, anyway). 

The last time I washed my car I hit on an idear.  I haven't had the time or energy to test it, so be forewarned, but as I looked at my car, covered in a dull haze of wax, waiting to be polished to brilliance, it hit on me--you could wax a TARDIS as well.  The unpolished bits would look dull and oxidized while the buffed out bits would be bright and shiny.  On the whole I think it has great promise. 

But I haven't tested it yet, so be forewarned...."Now I wouldn't go shooting at chests full of explosives..." 

This could also help with weather protection for the finish as well as adding the highlights (if that works). After all, the car wax, which theoretically can be used on any painted surface, will help protect the paint from the sun's UV rays that will lead to fading of your hard work painting (and "blackwashing" in the shadows), and it will also help the rain just bead up and roll off so it won't have as much chance to sit and seep through the inevitable bubble-holes and such in the paint, and then into any pores in the wood. And any wax that gets into the seams where, say, the stiles meet the walls or doors will also help the rain bead away rather than let it seep into those areas as well.

Sounds like a great idea, volpone! (I wonder if anyone had tried this before, and just not mentioned it yet?)

Dino.

I was looking into aging wood painting techniques and several YouTube videos suggested using a dry brush technique with a base color with a bit of white and apply as you suggested - on the edges and randomly. Lightly without overthinking it.
The wax technique was apply with an antiquing or slipping brush in the low points and rubbing off with microfiber cloth.
I tried the dry brush technique for the highlights and watered down black added to blue base for the interior of the frames.
I'm still playing with the shades in mine and picture quality is not the best, but here's where I'm at.

Looking good.  It looks like you used several different shades of blue.  That's something I've been meaning to do but haven't gotten around to that either.  It looks really nice.  As do the flatter and glossier sheens. 

Something I *did* attempt was to use either chalk or bits of drywall to rub along the edges to make a white highlight on them.  It worked OK.  But rain washed it off and the look wasn't impressive enough to keep reapplying it.