They can also be died at much lower temperatures, it just takes a lot longer. I dry mine by leaving them on top of a computer at ~35C for a week, I believe the air flow from the fans is important.

The color indicating ones are useful so you can see when they are dry.

At what ambient humidity do you do this? Where I am we are having a dry day at 45% humidity today. Tomorrow it'll be over 90%, and it'll stay between 50% and 90% through the weekend. I would expect that you need a more consistently dry environment for this to work