As a bottom, one think I'm always thinking about: will I be clean when I get fucked.
The good thing in Magnum is that we now have two intim toilet. A regular one and a luxury one where you need a noozle to use it. You can ask for the key at the desk.
As for the technique and tips. Here are a two pages to get more info:
https://www.sfaf.org/collections/beta/here-are-the-results-of-the-anal-douching-survey-in-san-francisco/
https://www.sfaf.org/collections/beta/anal-douching-safety-tips/
At the end of the day, if shit happens, shit happens. Be kind to your bottom or yourself and take a break. It's not the end of the world.