Im pre shading before base coat with tamiya flat black.For pre shading with brush what ratio of paint to thinner should I use?

I am not sure that is going to work...
First, Tamiya (acrylics) are hard to use with a brush. In any case, paint the preshadow as you would do for any base.
Second, the edges should be diffused so I guess it should be thinned after applied to soften them.
And third, the base paint over it should be quite thin to allow the preshading to be subtly seen under, which may require several thin layers.

All in all, I doubt the preshading is a technique for brush. But I maybe wrong.
It would be easier to paint the base flat and then add oils where the preshading would have been, as they can be controlled better.

I preshading with brush but only the figurine i dont think is a technique can work on AFV,you have to work in very thin layer and also Tamiya is the worse paint to work with brush

I only brush paint, I don't always pre-shade but here's what it looks like when I do .... I make the "black" pretty dark so it has an effect after drybrushing/blending the final colour over the top.

cheers
Brent

Shade



Blended



Final result

Can't brush paint Tamiya acrylics eh? Well this was painted with said Acrylics.

This was painted with Tamiya XF1

DSC_4030_2898 by Darren Greenwood, on Flickr

Thanks.I thinned the black to 1 part black and 3 parts thinner.Tried to post some pics from my album,but wont work.

Nobody said that,is just the most difficult paint to work by Brush compare to other brand

Brant great job!!...next time i try me to..