Id love to make some simple stencils to airbrush some Seraphon symbols onto my shields. Does anyone have any experience with this or advice for how to make a stencil and what material to use?
Uncle Atom has a video how to do that, see below. But the thing is: Those shields are pretty uneven so it might not work well. You are probably better off just doing them freehand. Practice on a piece of paper beforehand and then give it a go. It might not look perfectly accurate, but then: The Saurus who painted it are probably not that neat either, so you have a good excuse.
I would use the wrapping plastic from a household/food item, one that is stiff but easily bendable. Draw and cut out the shape. Note, leave lots of plastic on all sides, so you won't spray on the miniature by mistake. Then bend it carefully over the arm/location and spray on it. Wipe the plastic clean, and continue to the next one. The issue with this method, vs. using a product made for this is that depending on the location you want the shape on, you will need to do a tiny tidying up on most models, i.e. tying up the lines, etc. On the plus side, this is free, and it should be much easier than doing them by freehand. Though @bOdziO Wolf has a point, if you do that many by freehand, you will get quite good at it