Oh, boy. I'm totally overwhelmed. So much wonderful information and links. Jan, I knew I was saving those Altoid tins for something! I think my son uses that type of gum too.
I was surprised to read that tube watercolors are more transparent than pan watercolors. It's counter-intuitive. The only tubes I have are some I bought from Judikins, but I've never even used them. From the price, I'm pretty sure they are a less-than-student grade. She uses them for background techniques.
I'll be revisiting this thread, working my way through the suggestions and links. Thank you. Daria