Leaving the handrails off to weather the smokebox, boiler and firebox makes life a lot easier. The streaks and dribbles run down without being interrupted. They eventually have to be fitted though. They were made from 0.9mm brass wire earlier in the build and put to one side (=sort of lost in the clutter at the back of the bench). It's not so difficult as you'd think. The end of the wire was gripped in a pin chuck and the handrail gently pushed through the knobs while twisting the wire. It even works with the kink at the front of the firebox. You do need to be sure the handrail knobs are properly soldered in place. One coming loose at this stage would be...vexing.
The tiny collars for the ends of the handrails were turned from brass and fixed in place with the tiniest drop of low visosity cyano.
Of course the handrails need to be painted now to match the rest of the loco. They were brush painted with etch primer, then with the body masked, they were sprayed the tired black body colour.
Weathering on the bench is done with a right odd mixture of oils (Abteilung 502), weathering powders and various AK effects fluids. The weathering powders are some Carr's powders from ages ago. They're still useful, but these days I prefer to make my own from oil pastels. I have a few earthy and rusty colour pastels ( Talens Rembrandt soft pastels) that can be powdered by scraping a little off with a scalpel. They seem to stick better to the painted surfaces than the Carr's. I find that weathering powder beats the airbrush for some things. Handy hint - if you want to fix powders or granular material like coal dust or ash to the loco as part of the weathering process the best thing I've found is
MIG Ammo Pigment Fixer. It's very low viscosity, and surface tension fixative that you can apply without disturbing the weathering material. It dries clear and it leaves virtually no trace. It's probably a good fixer for ballast and ground cover as well. The other weathering goop worth having is
AK Interactive Wet Effects Fluid. It's kind of like a gloss varnish, but much less viscous. It dries with a very thin film thickness so doesn't stand out or cover the texture of the underlying surface, and it can be built up to various levels of wetness. Useful for water and oil leaks, and mixed with black weathering powder it makes an effective oily crud.
The weathering of the motion caused some soul searching. I had read Martyn Welch's approach and thought I'd do likewise...until I came to look more closely at colour photos of grubby 8Fs. Mostly the motion was caked with a layer of oil and road dirt. Usually quite dark and a little shiny. It was sprayed all over matt grubby black and grime, and then treated with a thin layer of wet effects fluid and black/brown weathering powder. The annoyance is that you have to keep moving the motion to get to everything. The end of the motor shaft was gripped in a pin chuck to make it easy to rotate the motion back and forth.
You can see the slightly textured, oily surfaces catching the light in this photo. A few streaks and highlights and cleaning off the appropriate parts of piston rod and slidebar will finish the job.
While my attention was focussed on all this, things had been happening outside...
From slightly frosty morning to white out in less time than it takes to filth up a set of 8 coupled motion!
There's still a lot to do, and it's still looking a bit goofy. The gross streaking will get toned down and blended in shortly. The tender chassis still doesn't have the foundation layer of undercarriage grot. The motion needs completing and weathering. Handrails to go on. Cab doors. It's a mixture of airbrush, enamels and oils. There are some things you can't do with an airbrush, and some things you can't do without an airbrush. 
