Interesting idea; I'd like to try these out and see how effective they are without their random pattern becoming repetitive.

Would have been nice if Yan had included some photos of results achieved with these.

Potentially, the top of the two could be used to apply "multi-cam" to a figure. If used as a spray mask.

I have the Ushi version,i want to use them on mi Millennium Falcon 1/72 i am doing now,on the Ushi web site you have some photos,i was thinking can be useful on random rust patterns or old paint discoloration LINK

Yes, that's the point. Can be used for dust also. Playing with subtle differences with base color you can achieve thoses effects. Vallejo, Liang, Tetra and others have their versions as well.

Yep...i think have so many use,also depend how far you keep from the model can change the finish,if you continue to turn the direction of the stencil its easy to random the pattern,some brand made them with plastic and others even thick paper,but after you have the problem how you clean it,the ones i have are thick PE,easy to clean with laquer