nail polish isnt for leather jackets. thats what material paint and decos are for the nail polish will eventually cack or just come off. im just telling you what would give you the best result to avoid having a shitty result or having to redo it.
nail varnish does eventually crack and getting it off can be a nightmare. i dont wear a leather, but on my cut off denim i make my own patches and stencils and i use acrylic paint, it also works on leather, i stencilled my friends leather jacket using acrylic paint. its waterproof and flexible. i also use in on jeans, tshirts and skirts :)
regular ol spray paint,,,its the technique you have to master,,cause it will come out looking shity if you dont know how to do it,,,well thats what my uncles used back in the early 80's,, oh and about the ''nigga incident'' anybody can use it as long as you use it the way he did ,,,there is a BIG difference from saying nigga and nigger,,''nigga'' is way less offensive if offensive at all when used properly that is LOL