One way is just to say 'His face registered disbelief,' or some variant. Maybe 'By the look on his face he clearly wasn't buying it.' If you really want to do it strictly through description of a facial expression I think all you need is 'One eyebrow went up slowly,' or maybe 'He gave him the suspicious side-eye.'
I'm with @Xoic. I think the easiest way would be to name the emotive reaction instead of describing the musculature. People will be able to picture it just fine if you say His face displayed utter incredulity. Although a combo is also an option: He cocked an eyebrow in disbelief.
Someone told me once "show, don't tell." I furrowed my brows above unblinking eyes, my nostrils flaring and an almost imperceptible curl to my lip. "Here, use this," they said and handed me a tissue. I should've just rolled my eyes in exasperation and muttered "sweet Jesus."
John's head cocked to the side as the divot in his chin deepened. His eyes hung heavy on Joseph while the young man explained where the dent in the fender came from.
Depending on your POV, one would have to be careful not to elicit the question, "registered disbelief to whom". If you're rolling with a 3rd limited, better to stick with the gory details.
I'm not sure how being in third limited changes things? I suppose the difference would be which character is the POV for the scene. Oviously it isn't the one whose face is being described—you can't see your own face and if you think somebody is lying, being the narrator, you wouldn't get that feeling across by describing changes in your own facial features—you'd just outright state that you were suspicious. It's the innner feeling of suspicion you'd be directly aware of, not what's happening on your own face. So the narrator (POV character) is either the other person in the dialogue, or a bystander observing them both. It's hard to see where there would be a problem with either of those scenarios (unless I'm missing something?) One of the big issues many beginning writers have is to try to overuse facial expressions and body language, in the mistaken belief that you should try to show as much as possible. This often results in a lack of some good solid telling where it would be the best choice, and in descriptions of incomprehensible writhing features and strange postures that don't actually convey the information the writer hopes they do. You want to use a sort of 'Occam's Razor' approach as the author—how can you get the information across clearly and evocatively using the least words? I don't mean the absolute least, but it's a matter of economy. If showing suspicion through facial expression and/or body language takes too many words or fails to get the idea across clearly and economically, that's when some nice simple telling is in order.
"His face looked like my landlord's when I'd told him he'd have it by the end of the month." ________ Edit for 3rd person limited: "His face looked like Mary's landlord's had when she'd told him he'd have it by the end of the month." Edit²: Going third person made me use too many apostrophes. It looks like they might roll off and cause unnecessary commas. Maybe, "He looked at her like her landlord had yesterday, when she'd told him he would get the rent by the end of the month."
If you want to humorous (if somewhat bizarre) approach, try ... ============= His eyebrows rose, saying hello to each other on his forehead. His mouth opened as wide as his wallet didn't. It reminded me of a bowling ball, perhaps in one of the city's shadier areas, where the other bowlers don't complain about tiny things like blood spots. =============
