That seems like a truck that doesn't get out much anymore. Rust is dark ... it's the fresh stuff that's a light color. I use anything that says Rust and various browns. Add a couple colors and a black wash. The nice thing is you can't do anything wrong. If you don't like a color paint over with another or wash off with solvent. Mother Nature constantly changes rust.
There is a paint fade at the bottom that was probably done with an air brush .. and it shows it. There is little evenness to rust and weathering. This is just as easy to do with a spray can.
The rust is as Harry says. Applying by hand is the best way to do it. Use various colors of rust and just put it on as nature does. Heavy at local holes and thinned like water to let run down like rain. Be sloppy! I faded the roof by a light rub with thinner a few hours after painting the body and very light over the rest of the body to fade it all over. No air brush was used anywhere.
This is a truck I did just as I described.
I don't have the kit and F50 photos show simple round tail lights with an inner circle of ... I assume some mesh and/or clear light. If I guessed wrong it's only because you didn't include a photo of what you need.
It seems a drill would be the way to remove the center. If needed you could then insert a rod that leaves the depth you need for the mesh.
If I'm wrong, it's because we love to fix imaginary problems here!
MM Multi-Tool I looked at this one for a long time and bought it when it was a lot off. I have found the vice to be the smallest vice for small parts and don't use any of the other parts, so is a bit expensive considering that. I never knew of an adjustable hemostat. Too bad my RN wife doesn't have access anymore.
I use all these things above, but I shy away from the half dozen hemostats have because they like to crush plastic. I also have a few small hand clamps that work well, especially for sanding.
I've used paintscratch.com for many of my builds, all for cars I've owned, both in a airbrush and in their spray cans. These were not metallic so can't comment on those. I've never had a problem and they apply and cover well.
I got behind viewing and it ALL looks spectacular so far! Everything just looks right.
One little tip from one who spent a career designing cranes would be to add small lengths of angle on the web between flanges as bump stops for the hoist. These are always there and will be a tiny detail that's noticeable. They would be right where you have some bolt heads.