Ex sign language interpreter here with a degree in ASL.
Only about 40% of sounds can actually even been seen on the lips. Many letters are actually hard to distinguish from others, like B and P/M, N, and NG /CH and J.
Even for a a skilled lipreader (Deaf or hearing), about the highest accuracy that can be achieved is between 45-60% when lipreading a bit of speech several sentences long. The higher end of that relies on: good lighting (not so bright as to wash out the person's lips, not too dark), the speaker staying completely facing the lipreader the entire time, the person not speaking too slow (that over-exaggerates the mouth movements and makes them confusing) or too fast, not having facial hair, not having very pale lips. Accuracy is also increased if the lipreader's is familiar/accustomed to the speaker, the topic of conversation is known, etc.
Over half of lipreading is educated guessing to fill in the blanks. And even that doesn't always help.
From what I've been able to find, there isn't any sort of training & certification program for people who call themselves professional/expert lip readers. It is much a talent (even for Deaf people...some are bad lip readers) as it is a technical skill.
Many people get the impression that lipreading is easy because they were able to lipread a short phrase (like between a coach and a player at a sporting event). But that is world's away from an entire conversation where the topic can switch back and forth multiple times.
hdi.uky.edu