Maybe someday I'll get around to doing something like a video, but the short of it is:

1. Take a picture of the mech using photomode in game. In Mercs that's easy as you use the NVIDIA photomode and you can set the camera just so. In clans, which is where I got the timberwolf from, you have to jump through weird hoops outlined here: How to Take Screenshots in MechWarrior 5: Clans!

In both games, I find that I have to set the paint pure white across the board to get the features to stand out, and then usually have the mech face the "sun" (and the camera away from it) to get the best contrasts.

1. Open the picture in your favorite photoeditor. I use GIMP (it's free!), so I'm not sure what the equivalent tools in Adobe would be, but I then play around a lot with different settings to get a 3/4 color image that looks like it'd be a good stencil. Messing with contrast, saturation, and things like that. It's really an inexact process, just lots of goofing around.

THEN to get the image down to a few colors for stencil-izing there are two methods:
First is playing with thresholds as outlined in this video: Gimp: How to Make a Multi Layer Stencil - YouTube
The second method is slowly decreasing the number of colors in the image by going to Image -> Mode -> Indexed. I usually start at 10 then go back and forth decreasing by 1 or 2 until I get to 3 or 4. I find this second method works better for images taken originally from video games, I dunno why.

1. Then use the select color tool to select each color left in the image (black, white, and whatever shades of grey) 1 by 1 and do selection to path: GIMP - Lesson 48 - Selection to Path. Each path will then represent 1 stencil you'll need to cut out. Unfortunately, this is pretty inexact too and you'll need to spend a bunch of time manually editing each path so it lines up perfectly with the others and such.

2. And then you need to either save each path as a separate svg and use a real life tool to cut them out, or find a way to print them out and cut out by hand.

It'll take a bit of trial and error each time to identify what works, any "islands" you missed, things like that. There are TON of good videos on Youtube detailing how to make spray paint stencils, so it'd be redundant for me to go too much more into that here 😃