Been a few years but here are some random thoughts I might look into. First of course do a test piece and see what works.
Could take a broom, dip it in a watered down paint and start sweeping the walls and woodwork. All sorts of brooms can come in handy from a wisk broom to street sweeping brush.
I thought I remember something about burning the wood first than staining it. Perhaps bleaching the lumber than staining it with a appropriate say white oak or bleaching stain would work.
The dirty water could work but so could a really watered down burn umber paint
wash, than perhaps another watered down
wash of black, than perhaps a
wash of something else in letting it dry between layers.
Bit of mustard
etc. Could just be hues and tints of your
base color two in washing it out at areas of the woodwork that needs to show wear or dirt.
I'm also a big fan of dry brushing technique for wood graining and not using
clear glaze between layers if I want an old look. For the initial layer, perhaps a bleached lumber look and a
clear latex
glaze over it. Than lightly
dry brush on the above colors which will cut down the gloss and flatten it out. Use of a semi-trashed brush so it don't paint well adds the
dry brush colors well. Semi-gloss
glaze as if old
varnish should still to some extent show
thru. Save some
base coat and
dry brush that in also in places or to correct for where the dirt becomes too heavy. This especially if wet mixing in the
base coat color in adding it while the layer below is still wet.
Another option might be to add some grey to a
hudson sprayer and do a fine mist all over the place - not too heavy at all - in fact slightly less than what seems enough. Tan do another spraying of black, than another of Raw Umber, than another of Burnt Senia, another .... as you work down the
line.
Could while each layer is also wet, take that above very stiff/trashed brush or broom and do some graining of the lumber with the mist of paint on the surface droplets. Harder brushing in some places, none at all in others. Otherwise the spray is used to add wear and washing out where the dirt was.
Again some random thoughts. A
book called "Recipies for Surfaces" might have otherwise a lot of other ideas.