Aqua Doodle hack

My parents bought Liza some of those Aqua Doodle mini mat books - you know, you color with a "pen" filled with water, and it reveals the picture underneath. We've come up with two ways to make them easier for a 2-year-old to handle:

1. The pen is great, but I'm afraid it won't last too long. We bought one of those things you use to moisten envelopes - like a small container with a sponge on one end. It reveals the pages much faster than the pen, it seems to be a little sturdier, and it was so cheap that I don't care if she ruins it. There's a little more potential for leakage, but hey, it's only water.
2. There are only three pages in each book, so we run out of pages pretty quickly. That's where the hair dryer comes in - set to low, you can make the colors magically disappear in less than a minute (maybe longer if it's sopping wet). I don't know if this will effect the performance of the coating on the pages long term, but we'll probably lose the book before it screws up the coating, anyway.

Anyone else have Aqua Doodle tips?

Oh, one more thing. One of our friends says that her daughter's Aqua Doodle floor mat is the only place their cat has ever peed outside the litter box. Has anyone else had this problem? She's had to start storing theirs on a high shelf in the closet to keep the cat away.