With the body colour airbrushed I opted to brush paint the remaining colours, it really didn't seem worth the effort of masking up when the job is easy enough with a brush. Smoke-box, footplate, hand-rails, and chassis frames got a coat of matt black but with a little grey and brown added to soften it. I find the Humbrol black doesn't harden well either for some reason, so mixing it with other colours helps get a good finish. The red bufferbeams were painted white first, to give a good base for 2-3 coats of red (which typically gives poor opacity). The inside of the cab was painted a slightly dirtied off-white. Finally a little dry-brushing of gunmetal on the handrails and cab steps gives a little life. The colour still seems bright though.
The first step of weathering is a dirty wash mixed of black and brown to taste, and well thinned. This is liberally washed over the model, and within a minute or two lightly dabbed or wiped away with a piece of kitchen roll or cotton bud. This leaves oily shadows around details like the boiler bands, and can be used to create streaks and accumulated dirt, it also darkens the colour (depending how strong the mix and how many coats are used) and can tone down a shiny finish. A little dry brushing can emphasise some streaks.
Looking better already, but for more depth and texture I use weathering powders, stippled on and worked in, then brushed off, with a stiff (cheap) paintbrush. Sooty black is applied to the tops of the tanks, boiler, smokebox, and cab roof, while a grey/brown is applied to the lower edges of the body panels and worked up. The direction of brushing can cause streaks, while working powers into crevices can add effect - such as the coal dust around the bunker and the gap between bunker and tank. Applying the powders is easy and quick, they can be repeated or wiped off to get the effect you want. At this stage the appearance is very dusty, and slightly over-done.
The final step is the coat of Testors Dullcote varnish. I find the stuff excellent, and easy to get a good finish. As can be seen the weathering powders are toned down a little, but also sealed so they do not mark or come off with handling. The varnish gives an even, flat, almost but not quite matt finish that is most lifelike I think.
Finishing involved assembly of the frames and the cylinders to the chassis, then the chassis assembly to the body, which was surprisingly fiddly. I checked the piston rods moved freely and coated them with graphite, and ensured the chassis was running smoothly at each step - at one point the flywheel was rubbing on the cab front but I don't think the chassis was aligned properly, there's now a piece of card between motor and cab to ensure it doesn't happen again. The cab roof was fitted with a few spots of PVA glue on the tabs I'd soldered to it, though it doesn't seem to want to sit perfectly over the cab sides, the vacuum pipes (which I'd painted separately) were added with a spot of superglue. Finally the worksplates were stuck on (with PVA) and a crew added - Dapol figures that I'd painted at the same time, and treated with a dirty wash wiped off to give shadows to clothing.
It's surprising how much the paint has darkened and the loco has taken on life as it has been weathered and detailed. The end result looks at home on my layout, and the Minitrains chassis runs sweetly too, so I can see this being a popular choice with the loco crews (even if it isn't clean!).
As a close, while I was checking the layout and locos for the Pevensey show this weekend, I couldn't resist a line-up of the locos used on the line. The Hudswell Clarke is centre front, with the other non-tramway locos, the centre and rear lines have the skirt-fitted locos. There are a mix of shades of green as well as other colours, and different levels of weathering, but somehow they all fit well together.