Microballoons in Acrylic Paint

Inspired by Robrex's builds posted on this forum, I have been searching the web high and low to find a detailed "how-to" on using microballoons with acrylic paint to get the effect Robrex has on the engine block of his Porsche 935 and other builds.

I tried a bunch of different air-brush types / mixtures / pressures but haven't suceeded. Does anyone (maybe even you Robrex - but it feels like asking a favor from God himself!) have a definitive guide for dummies on how to create that effect.