How do you show polite indication you’re not interested in a woman?

Ok for most of my life I never had this issue as I was skinny, unhealthy and didn’t care how I dressed.

But I’ve reentered the singles world recently, and went to an over 30’s singles event and my oh my how the tables have turned…. For the first time in my life it was the women who seemed more thirsty than the men… and I’ve just never, not even once, not a single time ever, been in a situation where more than one woman is overtly hitting on me… to the point they’re competing in an almost urgent and notable way … I’ve never developed the social acuity to navigate this dynamic before, it’s like there’s an ok girl offering to buy me a drink here and then a much hotter woman interrupting me on my way to the toilet to get my number and “get out of here for a drink elsewhere”… I’ve seen women naturally navigate such a dynamic as it’s there daily life…

I’m trying to think back on how brutally good women were at rejecting me all these years but it feels so difficult and mean to mirror that behaviour in reverse… not least of which women tend to take rejection more emotionally… where as a guy we just swallow it whole and bury it into our chamber of trauma and internal pain :D

I had one woman I spoke to briefly, see me walk out with a younger woman, and under her breath but loud enough to hear say “oh of course he goes for the tanned younger woman”… before trudging off… my friend who I went with heard it too and has basically been laughing about it for a week… I don’t really want that kind of drama, so I think I have to change my entire reception and converse to be less encouraging or something to set expectations when entering into a conversation…

Any other guys had to become more choosy and assertive later in life?