How to prepare?

My partner has spoken on his interest on trying anal, both of us have never done it before. We already do foreplay-type activities in that area, but I know anal itself will be a whole other ball-game. I really want to minimise any risk of “mess” or smells (if possible), I will genuinely do anything in preparation to avoid these things.

I also struggle sometimes with even just a finger, it very occasionally causes some aching afterwards, but I’m still keen to give it a go taking things further, if it doesn’t work, then it doesn’t work🤷‍♀️, won’t know till we try. Is there a safe and healthy way to prepare for something that much bigger?