Okay here's how I try to achieve the effect. Firstly, here are my materials I use:
EITHER: Silver metallic acrylic paint, Oil-based Terstors paint, or an acrylic paint pen. Whatever you use, try to stay consistent so all the paint matches. The silver acrylic paint is probably my least favorite, as it comes out a bit more flat and not as metallic as the oil based Testors or the paint pen. For the next tutorial photos, I use the paint pen. They you'll also need black acrylic paint, a container of water, paper towels, a natural sponge, some small brushes and a paper plate as a palette.
So the armor I was commissioned to weather is actually Doom Slayer armor he built. There were a heck of a lot more pieces to it than normal Spartan armor, so I marathoned painting this over 3-4 days.
First, start off dabbing black paint on ALL the raised edges of the armor. Naturally speaking, on any surface that sticks out or has an edge will see more wear than pieces that don't. There's a few different techniques you can use. I either dry brush it with the sponge or wet down the paint so it's more of a wash. Mare sure you break up the monotony of the sponge texture with horizontal or vertical strokes. Makes it more interesting and natural looking! If the paint is too dark, you can brush it off with the paper towel. Honestly with weathering, the messier, the better!
In this next pic, you can see how varying the texture makes it more visually interesting!
And here's the end result of the black weathering on a few pieces I made. Step 1 complete!
Okay! Now that step is done and the black paint is dry, over top I like to add very subtle hints of silver to show the raw metal exposed as if paint was worn away. I used the silver metallic paint pen for this step.
You definitely don't want any solid silver lines, but more broken up dots, dashes and chips. I'll also put in a couple cuts in the paint job with some broken, natural lines. Work with the natural texture of the EVA Foam too! If there are divots or holes, you can define them even more. I will often use my Dremmel to actually create scars and lines in the foam, which you can then outline in silver.
Here's a few nice scratches and scars I put in for some flavor
NOTE: This is an EXTREMELY time-consuming process so take your time and be patient! I find that if your foam crafting isn't that good (I'm still improving mine, personally), a good paint job can save a piece and make it look fantastic! If you make any mistakes in building your armor or cutting, you can embellish them and make it look like "natural weathering" too. I use this a lot when I cut too far into my foam with my box cutter lol.
And here's the final product! Like I said, it takes a pretty long time hitting every edge but if you play music or watch a movie in the background, you'll be surprised how the time flies!
And here's another piece I completed and some detail shots:
So yeah! You can also add mud, blood or dirt to add to it to make it even more weathered. After everything is dry, just hit it with a few coats of either matte or gloss Clear Coat to protect all your hard work. And that's about it! Hit me up with any questions or comments. I'm happy to answer and chat about the process!