this is where my armor experience comes in handy,
. its called a wash. there are two ways to make it ill tell you the way i do it first. i get a black acylic paint and mix it with water at about a 8 part water, 1 part paint. then you add about 3 part dishwashing soap/ hand soap. i use Dawn.... the soap it put in so you can let the mixture dry then you whipe a rag over it and it stays in the receeded areas, and whipes off the raised areas. the second is to get black artist, oil paint, mix it with mineral spirits (or whisky) will it looks like strong coffee and paint it on, letting it flow in the receeded details. this you dont let dry before whiping. it should be thin so it doesnt stick on the raised details. they both work but the first method i have found better for cars, you can also store it in a bottle. i hope this helps. you can also ask more in the armor section, youll get a million replies!