Karen - Glue stick are however, the world's most convenient sealer, and they are wonderful if you are traveling (and a collage-aholic, as am I.) I do buy them by the bulk! So you were right there.
Re: sealers - yeah, I'd just be careful there - practice a little. The kinds you paint on can make your work bubble. That isn't the end of the world, it can give your work "character" but it can also be disappointing. The kind you spray on can indeed change colors.
Worse yet, both have the capacity to "bleed" certain inks and paints.
Oh, and watercolors... How DO you seal watercolors? I've been so saddened by the smearing of watercolor tinting once an item is sealed....
xo - Chel
Chel