Google 'Historical Military Stencil Fonts' for a wide variety of sources. You can even order precut custom stencils for a surprisingly modest price.
You will need to visit an art supply store & buy stencil brushes that approximate the diameter of the lines in the font. The brush is not a conventional wave it back & forth brush. It is made up of very stiff bristles that are used to dob the paint through the stencil. A bit of practice is highly recommended.
Stencil brush & pouncer sets run $4 to $30. As with all art supplies, there is often a direct relationship between price & ease of use.
You will be surprised at how active & varied the modern use of stencils is.