Cinnamon?
Yes. You sprinkle some on, let it get into the nooks and crannies, then lightly brush it off. When you’re done with all your other weathering and you hit it with sealant, the cinnamon gets locked in place. Some of this is painted, some is cinnamon, but I think the result is very convincing rust:
Depth?
When I cut the background I also cut a copy of it out of heavy poster board. Using that underneath, I was able to raise the center panel JUST a bit and recess the louvered areas the same amount. Looks MUCH more interesting than the earlier panels that were only scored.
While we’re on tips - if you’re ever painting a flat piece (MDF is what I used here) and want it to look like something else (Stone? Plaster?)
What I did to get that rough texture for the “wall” was from several feet away, sprayed a few light coats of Scotch 77 adhesive (Spray Mount works as well) to build up a texture. I then painted over the top of that with (several different types of) black.
And the best part? My workroom SMELLS amazing… (Anybody got apple pie? I really want some apple pie…)
A note on weeding:
The key fact is that the masking sticky side will stick to itself far stronger than it will stick to anything else, even if the connection is less than a square millimeter.
This also includes the wood material. A secondary fact is that a very tiny pull will still pull the masking from the wood (or?) however slowly. Therefore, even if the masking is a quarter millimeter wide and will break if pulled too hard, it can be pulled below its breaking point and eventually pull cleanly away.
This means that even if hard to get started, if the tiniest bit can be pulled free and facing up, another piece of masking sticky side down will not grab anything hard except that tiny bit of flipped masking and it will grab that very well. If the piece is engraved with lots of tiny islands the sticky-side down masking will pull the edge of that island just enough to grab the whole piece and remove it.
Even something like this takes only a few minutes by first taking off the back and using that to easily clean the front…