Here are a few photos of the stages in loco weathering. In this case, the victim was Hornby's Peckett B2 "Westminster".
Sadly the photos don't follow each step but I'll try to fill in the blanks.
As started....
I'd already decided Westminster was going to be quite distressed. Therefore the starting point was adding rust, especially around the tank filler. Prior to this, the loco was sprayed with matt varnish to act as a key. Iron oxide weathering powder was used to apply the base rust. Now, I would use dark rust.
Now, you may see there is some white on the body. This is "blooming' from the varnish. I didn't prepare the aerosol properly and I suspect I eitger hadn't shaken it enough, the can wasn't warmed ( I normally stand in a bowl of warm water until just before use ) or it was a damp day........or a combination of all three.
Next, pre-shading was added to the loco using black weathering powder. I applied this to the rivets on the tank and seams to the bunker etc.
Rust was also added to the roof.
The bodywork was then coated in smoke weathering powder.
Also added is dark earth, applied mainly to the lower cab sides, bunker base and the underside of the saddle tank. This loco was weathered before I started using a quick blast of dark earth no 29 areosol, something I would now start with. The loco body would now be sprayed at "stage 1" from below to create a dusty appearance to these areas.
At this point, a light dusting of varnish was applied, to seal the work thus far.
I wanted a faded appearance to the paintwork. This was done using sand weathering powder applied in small quantities to the areas to be faded. I decided to work in "panels".
Sand powder, like white will go a long way so only use a little at a time, adding more if you don't arrive at the desired effect first time.
This stage takes time as you work from the centre of the "panel" out. This creates a lighter centre and dark edge..........or it should.
You can also use a bit of white foe extra contrast but it needs careful use to avoid it jarring.
And this is how it ended up.....
Rob