I've made a quick tutorial on how to get vibrant looking gradient undercoats for your models, with a method that is quicker and easier than simply painting colour ontop of black/another colour.
In the tutorial I use a Drukhari Ravager as an example:
Read the full article here:
http://finnhammer.eu/2018/07/20/238/
Bookmark the page if you're into following hobby content. The progress of my Drukhari army will also be posted on the Finnhammer -hub.
I hope it'll prove useful to someone. Works on all vehicles and all colours.