One of the best things about travel is getting to meet other people. And every now and then, you luck out and meet someone who starts a conversation that leads to amazing travel advice.
I didn't know about the talcum powder trick. The $20 idea is good but I'd also say keeping a crisp $100 somewhere is also a solid practice. One time in Frankfurt I couldn't get one of my bills exchanged because it was an older style. Now I try to bring only new cash and use my cards whenever possible.