This is unlike the question How to write good erotic scene?, which refers to a sub-plot of a novel in which two characters had sex. There the accepted answer essentially evades any detailed descriptions of the act, by focusing on appearance, or feelings and specifically NOT about genitalia or the actions involved in having sex. Other respondents suggesting similar methods of "hiding" the sex scene, stopping with a kiss or embrace, and jumping to a point after the sex has happened.
In erotica, the whole reason the reader is reading is for a lengthy and detailed blow-by-blow sex scene, that is the nature of the genre, and the treatment of sex in a novel or R-rated movie defeats that purpose. The reader wants a fully imagined sex scene, genitalia, penetrations, orgasms, fluids, the whole thing. Perhaps for masturbation or perhaps as a scene to reenact with a willing partner for role-playing fun. (If you are put off by these purposes, this question is not for you!)
All of that said, I write erotica. Typically these stories have a setup and scenario which I can describe quite well. However, once I get to the... main event... I find it much too easy to fall into the trap of clichés about crashing waves and rolling eyes.
I think perhaps other writers can provide a good way of thinking about such scenes to accomplish this, or perhaps ways in which this is similar to other writing tasks for which more advice exists.
What approach can I use to tackle writing long and detailed explicit sex scenes without turning away, that are varied and will sexually excite my readers without using silly similes or boring my reader?