Use the Mid band for peaking or High band for shelving. Both the Fruity Multiband Compressor and Maximus can operate in either mode. There are two main modes you may want to de-ess in, peaking (a narrow-band) or shelving (starting at a given frequency and upward). So if you have a multi-band compressor, you have a de-esser.
Most good de-essers are simply band-limited compressors repackaged and labelled so they can be called a ‘de-esser’. In this tutorial we explore three methods for de-essing vocals in FL Studio using the tools supplied.