I may not be the best source for weathering, as I do things backwards. Most will apply weathering where they want it...I paint the entire area solid, then remove paint as I go, leaving behind what I want. Even with the smallest detail brush, in N scale, I found that this method was easier for me. That said, I personally didn't like the results with India Ink. I think the wash is hard to control, and can leave a spotty finish. The good news is, it's easy to remove if you don't like what you've done.
Here's a paint list that I use for engines. All paints are Floquil:
- Oily Black - Used for greasy spots, like fuel and oily spills.
- Grimy Black - All purpose yucky/dirty greyish black grime and road dirt.
- Roof Brown - A dirty brown color, which is also great for use on boxcars.
- Rust - Not a true rusty color by itself, but is good mixed with other colors.
- Earth - A light tan that reminds me of mud.
- Dirt - Greenish/brown color that is best used in moderation.
- Aged Concrete - Also great for buildings, this is a dirty greyish/white color.
- Rail Brown - Dark brown color with a hint of rust.
First, you have to make a decision...and it's an important one. How much weathing will you apply? I have 3 levels of weathering:
- Light - Perhaps it's a new engine, or recently serviced. These will still be dirty from use, but won't show significant signs of rust and dirt.
- Moderate - Average road useage. This engine has been in service for awhile, and shows signs of neglect and age.
- Heavy - Used and abused. Lots of rust and dirt.
I usually give the whole thing a light coating of grime first. Say goodbye to that pretty engine! Use a wash of Grimy Black and thinner and coat the whole engine with the wash...be sure to only do 1 side at a time. The wash should "stand" on the surface. Use a soft-bristled wide brush and apply the wash. Clean it off with thinner, dry it on a towel, and using the same brush...absorb the wash. This will soak up the standing thinner, leaving behind a layer of paint. I then take a stiff, short-bristled brush and scrub away most of the paint. What's left behind is a thin coating of grime over the whole loco. The wash will collect around details, darkening them, which is what you want. For an SD45, you'll want to darken the fan and radiator covers with another coating. The best thing you can do is find pictures of real engines, and try to copy them.
You'll also want to apply some Rust to the couplers and high useage spots like handrails and steps. A little goes a long way with Rust. For fuel spills and drips, use Oily Black. This paint can be hard to see, especially on a black engine. But if you apply the all over dirt technique using Grimy Black as described above, it will show up really well.
The roof will also need to be weathered. I found that by painting a wash right down the centerline of the roof and lighly drybrushing it towards the edges works best. I'm also a fan of drybrushing, which is very time consuming, but the end result is great. Above all, trial and error is going to be your best friend. What works for me or the next guy may not work for you. The MRR book "Basic Painting and Weathering" is a great tool, so pick that up if you can.
Good luck! :thumb: