Lt.Soundwave wrote:Thin with windex or alcohol. Thin coats are awesome

I really like the ceramite white coverage of
GW's base coat. It is a great deal brighter then it first appears to be as well.
Use an airbrush thinner. There are plenty of brands out there (Vallejo, Liquitex, Golden...). Windex is bad for you and alcohol can have undesired effects with paint some times.
But to answer your question, for pure white, prime with white primer and then add a coat of white paint. Vallejo Model Air white is fantastic. Also, what effect are you going for? Because if you require shading, there are various ways to do it using different base colors.