Dave,

The following may help you to decide - and hopefully
will make the process a lot easier to do and at the same
time end up with freight cars you like more.

I have a "standard practice" that includes touching all of
the handrails, grabs, corner brackets, drop steps, brake
wheels, couplers, cut levers, etc., etc., etc. with a brush
with "whatever shade of 'Tuscan' I happen to mix up that
day". I don't try to 'cover' them ... just a dab/stroke/run
the brush over it here and there.
I normally start with about 4 to 1 Tuscan to some shade
of Mineral Red/any shade of burnt umber/burnt sienna/
red umber etc. ... but I don't pay a lot of attention to the
number of drops of each color and let whatever I can
reach easiest be as much my method as anything else.
And I will frequently add a couple of drops of grey or black
or white or a mustardy yellow (CNW or reefer yellow). I do
not have a 'formula' that I use every time ... other
than starting with some shade of "tuscan".

But the key point is that I do -not- want it to match the
body color. I want it to be "a few shades different".

When you do this - the result is a handrail/grab that looks
like the right color ... but it "stands out from the body".

Background - most of the time when you look at a real
freight car there is a highlight+shadow effect going on (yes,
even when it isn't in full sun ... *G*). The details tend to be
more noticeable than any factory paint car -model- that
you see on any layout any where. To understand what I
mean go fish out any unweathered Kadee box car you
have and hold it up next to your computer monitor that
is on a color picture of a real 'tuscan' box car.
Unless you use extremely high quantities of light on your
layout you just don't get those shadows. And even if the
shadow is there ... the size of the grabs/handrails/etc. are
so small that our eyes don't pick them up.

So my "just a couple of shades off of the body" ... simulates
the "shadows" - and my goal of having the detail part look
correct - but "pop out" without being too big a difference
is achieved.

When trying to add some 'rust' to detail colors other than
freight car red ... I like to thin the paint out until it flows
(runs) into the corners ...
- Jim Betz

P.S. I like to go back after doing the detail weathering and
shoot what I refer to as "blending coats" of some
shade of grimy black, mud, etc.
I have found that since I started doing the brush
detail weathering (which includes washes, etc.) that
I use a LOT less paint during this blending process.