Well, I finally tweaked my flat future mixture thanks to some of the suggestions in this thread. I'm now takeing 5 parts Future, 2 parts Golden fluid matte medium and 2 parts 99% Isopropyl alcohol. The alcohol let me lower the pressure by about 5 PSI and the spray is going on much more thinly and evenly. So far, no clouding on any test pieces. It's not 100% dead matte. 3 drops of the matte medium got it to be really matte.
During my first test I forgot to take the protective cap off of the front of my airbrush. The end result was that it spattered the toy tank I was testing on rather badly. On the plus side, I got to see what thick sections look like. The look a little bit glossy-- like a satin finish. Atleast I know what the sheen of multiple layers will look like.
It looks like Tamiya flat base is a little better at making Future flat. It takes less of it to achieve the same results as the Golden. Next time I'm in the local art shop, I'll grab some W&N Matte Varnish and give it a try.