I'm not sure. He's been inactive for a while. Which sucks. I suspect he applies the highlights with a brush and adds water to desaturated the paint so it fades better. (which is definitely something I'd be afraid to do.) I have some experience with using various mediums. For example, [url=http://farm8.staticflickr.com/7311/9713687746_fce4933ce0_b.jpg]this sketch[/url] (which I can't finish due to having lost certain markers =[ ) was done with markers,colored pencils, and acrylic paint. But foam is a lot easier to do than clean highlights that fade smoothly.