Ann Marie here! I had hoped to get our Old Faithful pics scrapped in time for this post, but we were barely back from Yellowstone when we turned around and left town again! We just got back today, and I thought that I would instead showcase some simple water-based products.
1) Watercolor crayons. These are so much fun! These are some cheapy ones a friend of mine received as a silly gift... She isn't the crafty sort and didn't have any interest in them, so she passed them on to me. I hadn't played with them yet, so tried them out. I just colored across a stamp...

misted it with water, and presto. A beautiful, elegant, floating image. (You can get a similar effect by inking up a stamp with Distress Inks and spritzing with water.)

2) Twinkling H20s. I loved these when they first came out--the glimmer, shimmer, and fluid graceful beauty absolutely drew me in. I feel like I am still exploring how to use them. I've "painted" in designs with them, created color washes on backgrounds, used dots of concentrated color to create a 3-D effect... but I wanted to do something similar to the above technique, that would build off of the fluid nature of these paints.

So... I watered up each paint pot, swiped big strokes of each color across the stamp in different places, allowing them to overlap...

And voila! A subtle, shimmery background image. (This would work with any type of watercolor paint, you just won't get the twinkle.)

3) Watermark ink. Yeah, okay, so technically, there's no water involved here beyond the name. And this is a very basic stamping technique (one of the first I learned!). But that's okay, it's still a gorgeous look I love to whip out once in awhile. (Simple is best in my book.)Simply ink up your stamp with a watermark ink (such as Perfect Medium or Versamark), press, and... you're rewarded with a tone-on-tone effect, with your image a shade darker than your cardstock.

A few tips with these techniques:
1) Water-based techniques tend to result in a subtle, careworn, or vintage flair. Use accordingly. I find loosely drawn or distressed images work well.
2) If you're coloring or painting directly onto a stamp, I've found that rubber works better than polymer.
3) Protect your work surface and surrounding projects! Nothing worse than a wet project when you weren't planning for it. :-/
4) Use a non-water soluble ink to stamp over the images produced with a water-based technique. Especially if you are impatient like me and the image may not be completely dry! :-) Pigments are okay, best are archival inks like Brilliance, or something like StazOn. I don't recommend dye inks for overstamping these types of images.
5) Have fun, relax, and go with the flow! It may take multiple tries to get the impression you want. I found it was easier to stamp until I found one I liked, then cut my card from that than to stamp onto a card already in progress. ;-)

Now, go play in the rain!