I don't have facial blindness and rarely have issues picturing characters in my head, usually it's only when I'm not connecting with the story or characters much.
One tip I can give is imagine and "set" a style for each character based on personality. What do I feel this person would wear? Are they grundgy sounding, does this person seem like someone who wears lots of accessories, do they seem like a stuffy person who only wears khaki shorts, maybe they have a particular hairstyle or hair color, or the cadence of their speech is particular. For easeir times imagine them always wearing that same outfit like a cartoon character.
I don't have facial blindness and rarely have issues picturing characters in my head, usually it's only when I'm not connecting with the story or characters much.
One tip I can give is imagine and "set" a style for each character based on personality. What do I feel this person would wear? Are they grundgy sounding, does this person seem like someone who wears lots of accessories, do they seem like a stuffy person who only wears khaki shorts, maybe they have a particular hairstyle or hair color, or the cadence of their speech is particular. For easeir times imagine them always wearing that same outfit like a cartoon character.