These sets are quite nice (I've tryed a couple). These are from AMMO (Mig Jimenez new company - He no longer has any conection with MIG Productions.
AMMO's webpage has many tutorials, showing how to apply washes and pigments. Here is the link:
https://www.migjimenez.com/en/
and here is the list of tutorials (downloadable PDFs):
https://www.migjimenez.com/en/content/7-downloads-ammo-of-mig-jimenez
You can also find more information in their regular publications (The Weathering Magazine and The Weathering Aircraft), but do not take this tutorials as gospel and experiment with it yourself.
I hope you find it usefull!
Cheers
Marco Preto
http://mpminiatures.wordpress.com