I'm wondering if there is a tutorial somewhere to show how to paint the area of fuel emission from geometry. Like if I have a log and only want the end on fire, how do you paint this area of effect?

there are a number of ways to do this. paint where you want the fuel to be. then you can scatter points on the log and build fuel from these points with a fluid source sop. or you can use a volume from attrib and build a fuel volume from the attribute you painted. you can really use any method to define a volume and as long as its called fuel, or whatever you call it is referenced in the sop to dop bindings of the source volume dop, it will work.