I don't believe they 'advertised' in Bible times,
But if they were bleeding/menstruating they had to keep out of people's way or, if they HAD to go out, they would have needed to tell someone what was happening so that no one touched them.
but they were strictly careful NOT to be in a place or situation where they would make someone else unclean,
Except for the woman with the issue of blood who was desperate enough, and Jesus who was compassionate enough, not to let it make a difference.
He didn't tell her off for breaking the law, tell the crowd that dozens of them had been made unclean or shout "unclean, unclean".
She broke the law by even approaching Jesus, never mind touching him - yet he healed, and didn't rebuke, her.
They believed it made the woman unclean BECAUSE it does.
You might believe that; hundreds of people don't.
This has not changed, as God's Word never changed.
No. GOD doesn't change, but he sometimes works in new, and different, ways.
Once, people had to offer animal sacrifices to atone for their sin; they had to take these animals to the priests at the temple to be killed. Jews don't even do that today - they have no temple for a start. Gentiles certainly don't do that, because we have Jesus. God sent his Son to be a sacrifice once and for all for sin. He no longer requires animal sacrifices.
God told Isaiah that he would work in a NEW way. He told Jeremiah he was making a NEW covenant.
If you believe that Jesus fulfilled the law and the prophets and has saved us, yet still, on top of that, want to obey all the Jewish food and hygiene laws; that is up to you. Most of us don't want to do that.