Oooooo, this is great information!!  I just bought a  set of model colour a couple weeks ago.  I haven't had any probs brushing it so far but did notice different viscosities of various colours.  Scott has provided an explanation for that.  Once thinned though, it worked great.  I'll defo try the future!   Thanks.  I've never tried the Citadel, but word on the street (at the local gaming   club) is that they are excellent paints.  JMac's right, experiment!!