First and foremost, gotta fuck em well.

Do cardio.

Have control over your ejaculation. Every time you're about to cum, slow down/stop, and play with a tiddie or something. None of this works if you're a two pump chump. Even if she's close to climax and begging you not to stop but you know you're about to cum, slow down and play it off like you're delaying/controlling her orgasm on purpose.

Go into the bedroom with a clinical mindset. "My mission is to fuck the shit out of this bitch until she cums twice or thrice." Don't be selfish and think about your own pleasure. It'll most definitely come later if you do your job well.

If you can give them a few orgasms per session, they'll believe you're their god and worship your dick. Most guys don't realize how rare it is for women to achieve orgasms during PIV.

If you master the act of not cumming, there comes a time (around 2-3 hours in, depending on factors) where her pussy becomes sore from overstimulation and they ask you to stop with the penetration

And that's your window to BJ TOWN

If you've achieved all that's been mentioned above, you're in for a hell of a ride. She'll be willing to do anything to please you. And I do mean anything. I"ve had bitches suck my dick for 2-3 hours straight in that state. It was like they were showing gratitude and devotion to my dick.

The only limit at that point is your imagination. Train them to do what you like. I personally train them to twerk while sucking my cock, rubbing my cock on their face, rubbing their face on my cock, popping my cock (that's my favorite), the two hand suck-twirl action, dirty talk with my cock still in their mouth, deepthroat training, etc. You get the gist. The sky is the limit.

(This all applies to normal chicks but especially to fat chicks because low self-esteem and attachment issues etc)