How to make a smooth crème brûlée top
You should pour a little heap of sugar on top of the dessert, then swirl the dish around so that the surface is evenly covered with sugar.  anything that's left over, dump on to the next one (or into an 'extra sugar' dish).  This is important - there shouldn't be any loose sugar on top.  

Now use the torch as long as you need to, although in my experience it shouldn't have an absolutely 'smooth' finish - there should be some texture.  Also, too much torch and the sugar will go past caramelization and just be burnt.  

Source: worked in a fine dining restaurant for ~5 years and did this quite often.