I used humbrol's own thinner for acrylics and this worked well. The paint sprayed on nice and smooth too. I also tested lightening the base colour with some tamiya white which actually worked so I will spray over a lighter tone next before tackling the camo pattern. I haven't used humbrol paints for a very long time, in fact the last time I did I was still using enamels.
The elefant has also progressed with some light chipping going on, the spare tracks fixed in place & a gloss coat as well. Next will be filters & washes so I'm now back on schedule with this one.