If I had a dog excessively licking my other until it was raw, there is no way I would allow him to get anywhere near.

Two options, before your other dog becomes infected by a constant open wound.
Firstly have you tried giving Charlie a nice juicy knuckle bone or chew to occupie himself with instead, or secondly I would muzzle him until the wound is properly healed.
Is seperation really impractical, I'd even shut him in the bathroom with a dog bed and water if it does not stop.
Perhaps others will be able to recommend a harmless spray or something that tastes disgusting to put him off once the wound is healed, but in the meantime, just go buy a muzzle if you can not seperate.