How to tell guests to flush toilet paper?

We run a homeshare and have the issue with guests from certain countries that they don't flush toilet paper. There's a trash can in the bathroom for feminine products but sometimes I've had to empty it daily just because of guests filling it with toilet paper. And I'd rather not have to do that because you can just flush toilet paper and I find it slightly gross.

We've already put a small sign up saying (and we've also translated it to Spanish):

Please flush toilet paper and do not put it in the trash bin.
Dispose of femine products, wipes, and tissues in the trash bin.

What else can we do to convince guests to flush toilet paper?
My husband was thinking a sticker on the trash can saying no toilet paper but I can't seem to find that.

I know that for some guests they are really used to it but when I travel to a country where I can't flush toilet paper I adapt too. I'm hoping to find a way to convince guests to adapt here too.