I think what is most important is asking yourself what it is about titfucking that turns you on. Get granular, and explore that through your art. I think thats what sets apart titfucks drawn by people who are just checking a box vs folks who are real perverts for boob sex. It helps you picture what it is you want to depict, rather than a symbol for it, if that makes sense.

But also: yeah, please use refs. Look at photos and video of your subject matter. You dont have to copy but you MUST observe.