I don't have any experience with the Illuminate Glimmer Watermark pad, so I can't comment on that.
However, I like using the Frost White Shimmer Paint to create the look of snow. Here are links to a few examples:
dynamic tagged penguin by PH in VA - Cards and Paper Crafts at Splitcoaststampers
hello deerie - HYCCT1117 by PH in VA - Cards and Paper Crafts at Splitcoaststampers
Christmas 2009 by PH in VA - Cards and Paper Crafts at Splitcoaststampers
For each of those, I used a paintbrush to add the paint to the cardstock. For the tree card linked above, I used the paint with a fairly dry brush because I wanted the green of the trees to show through. Even though I made approximately 75 of those cards, I'm using the same bottle of paint I bought then, and it's still about 2/3 full. (In other words, a little paint goes a long way.)
I've never watched the clock on it, but the paint doesn't take too long to fully dry - maybe 15 minutes? But that could also depend on how thickly you apply it.
I've tried using a paper towel to dab the paint onto a stamp, but didn't like the results when I stamped the image. I think the paint is too thin and got the rubber too wet to make a clear imprint. I didn't think to try it the other way - tapping the stamp onto the saturated paper towel. I've only tried this with rubber stamps, so I don't know how much different the results might be with clear stamps.
I have not tried using the paint on surfaces other than cardstock.
I bet it would look pretty applied to flowers for a wedding or anniversary card.
I realize my experiences are pretty limited, but hopefully you'll find this information helpful.