The fan brush is a good choice for applying illuminator and contouring, mainly due to its longer format and fewer bristles. However, it is not the only option.
The bevelled brush is also an excellent choice, as it has uneven bristles with increasing direction, which ensures a smoky and natural look, a must for good contouring.
In fact, in the case of contouring, the bevelled brush ends up being the most indicated, exactly because it guarantees greater delicacy and a more accurate stroke. The fan is like a plan B, breaking the ice.
However, in the case of illuminator, the fan comes out ahead, and the beveled goes to the background. This happens because the use of illuminator requires a lighter and more delicate brush, especially due to the shine, which requires care.