The face of disgust is commonly drawn-up into one big pucker. The lips curling into a snarling frown, the nostrils flaring, the cheeks pushing up to squinting lower lids and a furrowed brow. There is a moral type of disgust (societal) and an infectious disease type of disgust (primal). You can achieve the primal facial expression easily by imagining a really horrible smell.
Asymmetry adds appeal to any facial expression. Is the face shape more extreme on the side of the face nearest the object of disgust, or is it more extreme on the side furthest away? Which makes more sense for the situation? You may want to flinch or turn your face and/or body to get away from the disgusting thing or retreat from it.
Watch out for over-acting. In cartoons we tend to exaggerate emotions and make things bigger than life, but if the disgusted reaction is too over-the-top for the situation it can make the performance seem insincere. Maybe the scene calls for a performance more subtle and nuanced. Over-acting can happen when you are trying too hard to convince the audience of what you’re feeling rather than literally feeling the emotion and reacting honestly. A good acting reference performance is more likely to come from allowing yourself to feel the disgust and letting that feeling inform your acting decisions. Rely on your own personal life experience with feeling disgusted.
Pro Tip: Watch out for over-acting. Over-acting can happen when you are trying too hard to convince the audience of what you’re feeling rather than literally feeling the emotion and reacting honestly.
Timing and Intensity
Consider timing and intensity. There are varying degrees of disgust from a slight curl in the lip, to extreme wincing and nausea. Is your character suddenly and violently filled with disgust by tasting something horrible? Or maybe it is a slow build over time as the character is listening to a terrible story and realization slowly sets in. Maybe the character is feeling disgust that later gets mixed with a little surprise, excitement, or disappointment.
I got to help out with the emotes for the video game State of Decay 2 by Undead Labs, and the clip below was a fun one to animate. The character flashes a look of disgust just before the mocking smile & condescending slow clap, and when he drops his hands, his face also drops with a look of contempt. The disgust, mocking smile and contempt facial expressions work together to flesh out his disgusted emotional state. When I was acting it out I was imagining that he was disgusted with someone who had accidentally let the zombies in.