Hi blackdesert,
This is only my opinion, so do your research.
if you top, make sure you wash with soap and water after each encounter, people underestimate cleaning afterwards.
if you’re oral, use alcohol based mouthwash after each encounter, the alcohol should kill a lot of microbes, and lower your chances. Gargle at least a minute.
If you bottom, you can lessen the possibility of stds, by inserting a silver colloidal gel into the rectum. I’m not saying this works perfectly, but it can act as a protective lube since the silver is a natural antimicrobial.
another in coconut oil, it has antimicrobial properties.
or any thing you can research that can be inserted rectally without causing harm. Avoid alcohol as this will be absorbed through rectal lining and can cause possible alcohol poisoning.
douche with saltwater afterwards if you can. A lot of microbes don’t like salty environments.
best