Here we have a simple hot coal material.
Step 1: Click on the object you want to use with this material. Add a “Multiresolution” modifier to the object and click “Subdivide” 3 times.
Step 2: Sculpt the surface. The crevices in the surface will partially control the “hot glow” effect. Once you are happy with the shape click “Apply”
Step 3: Switch to vertex paint mode. Click “Paint” then “Dirty Vertex Colours”. Adjust the values. Note how the shadows and highlights work on your objects topology.
Note: You can quickly paint more dark or light areas manually.
Step 4: Use A setup like this one. The “Attribute Node” with “Col” entered into the text box brings the vertex colours into play. Quickly preview of your results by pressing “Shift-Z” or a test render”F12″.
If you like the results, Great. If you don’t, well you can always delete the Vertex colour values (Col) and repeat step 3.