Paper stick is most used in the classic pencil art for the smudge or toned down pencil strokes. It is made of the rolled paper with sharp edges. As many other artist materials and tools, this one could be also used in the plastic modeling.
Finished model get more realistic if it get some of the weathering, dirt as well fade of the surface. This is the part of the real life where the airplane are under permanent exposure to the sun light, ground personnel maintenance, leaks of the fuel and oil, influence of environmental surrounding [like salt, dirt from soil and so on…]
Modelers used various methods to represent this influence on the models and paper stick is good one for this. This stick is best for use with powder material like the graphite pencil in powder or drawn lines. How to use is simple- you can dirt the sharp point of stick with graphite powder, chalk or even coal and stick it over the panel lines. Also you can draw lines with pencil and smudge it with paper stick. As well it could be used for wide shading with the side of the cone and this is good for the area behind the exhaust on the piston engine.
Worth to try!