Be clear about what kind of casual relationship you want. Friend with benefits is not a real date. It's all about physical contacts, openness, and ultimately, just for fun. If the person having sex with you doesn't care about your needs, or you don't like it at all, then it doesn't make sense to do it. You are free to explore and experiment. Through this casual affair dating relationship, you will realize that good sex is physical and mental health, so go ahead and try it.
FWB is an affair dating, not a secret dating. Don't let anyone judge you or make you feel weird about what you are doing. Your family may not understand. An acquaintance might think this is promiscuous. Some of your friends may even suspect that friends with benefits relationship is just a transition and not a relationship. You can't expect everyone you meet to understand you, but you don't have to listen to others telling you what to do, and what not to do. Live yourself, pursue your favorite feelings and be confident in yourself. After all you know what you are doing.
End this fwb dating in a proper way when you notice that there is a feeling developing between you two, especially when you don't want it. Just break it off maturely. You must end this adult affair dating relationship in a correct and kind way. Even if you are not technically wrong, because you always know what you want, you are all human, and sex feels good, intimate and cute, which sometimes makes you feel closer to someone than you want. When you realize that the adult friend wants to find more things in this casual hookup relationship, and these are things you can't give, then you should never date this person. If you don't reciprocate their feelings, but you owe each other a clean break up, this will not hurt their emotions.
If you are the one who ends the feelings and relationship, don't feel bad and forgive yourself. Remind it again, you are human. You will find that you actually like this person more than you realize. If you really like him, you should let him know before you decide whether to take this tinder free relationship to another level. Of course, they may like you too, but you should also be prepared that they may not like you. Regardless of the outcome, try not to care too much. If the other adult friend finder can't respond to your feelings, then go ahead and don't associate with them anymore. Respect your emotions and don't just stay there and make them or yourself believe that you are super cold. It's all for honesty.