I'm working on a skin shader with HDRP Shader Graph and looks like I don't understand some basic concepts... Let's say skin should use two specular reflections: basic one with smoothness = 0.45 and second one with smoothness = 0.65. They should be mixed additively. Is it possible to achieve with Shader Graph? There is some option called "coat" on a lit shader but it's just replace basic smoothness with completely glossy reflection. How can I additively mix two reflections?