Subby obedient girls needing permission to swallow cum is not hyped up enough. If you tell your sub they need your permission to swallow your cum lots of fun can ensue:
Make them show you all the cum they earned from blowing you. Make them shut their mouth and show you again later.
Make them wait quietly for a while with the taste of you on their tongue.
Make them gargle your cum until you're satisfied with the amount of bubbles they make.
Let them hold their cummy mouth open for you to spit in for a while.
Fuck them and cum in a condom (a non-lubricated one). Give them permission to suck your cum out of the condom.
Cum in their mouth and secure a ballgag in their mouth after. Fuck them with a dildo while they drool saliva and cum all over themselves.
Tell them to swish your cum around in their mouth like a mouthwash before swallowing so they'll taste you for hours afterwards.
Cum straight down their throat when you want to, forcing them to swallow whenever you want them to.
If they're being too mouthy and disrespectful, fuck their face and don't give them permission to swallow. If they try to speak, tell them it's rude to talk with their mouth full and they will wait. When they're ready to say sorry, let them swallow and apologize.
Cum in their mouth and gag them with their own panties. Later, make them wear those cum soaked panties.
Cum on a bowl or plate and make them ask for explicit permission to lick it up and swallow.
Wash down their mouthful of cum by pissing in their mouth.
Make them complete a task or chore while having a mouthful of your cum.
Have them keep their mouth open after you cum in it and finger their mouth.
Reach in and grab some of your cum so you can smear it across their face.
Cum in their underwear and give them permission to lick it off.
Make them describe the taste to you and the different notes they perceive in your cum like they're tasting a fine wine. Do not allow them to swallow until you're satisfied with their taste analysis.
Tell them at the beginning of a blowjob you're requiring them to swallow immediately or they won't get permission to swallow it at all.
Make them spit out your cum into your palm so you can slap your cum across their face or rub it into their chest.
Cum in their open mouth and have them suck on a salivating mint (like Flintt's Mints) afterwards so they drool their saliva and your cum all over their face and chest while you stimulate them with your fingers and a magic wand.
Casually remind them in public they're so obedient and well trained for you that they have to wait to swallow their treat like they're a pet at a dog show.
Obviously not every option above will be for everyone. But the possibilities are numerous and making your super obedient sub wait for permission for things they can already do themselves is very humbling and enjoyable. Train their deference and docility and have fun doing it!
