II. Top layer thickness increasing
Increasing the top layer thickness is the easiest solution. Most common softwares will enable you to do this. Check the advanced section, under the 'Bottom / Top Thickness setting'. Usual its set up fot 6 layers of material normally and up to 8 for nozzles under 0,4 mm. If your layer height is therefore set to 0.1mm then set the 'Bottom / Top Thickness setting' to 0.6mm. If the effect of pillowing still persist then increase to 0.8mm.