When I use chalks and Perfect Pearls I seal them with Krylon Preserve It since I use them in my scrapbooks as well as cards. I find it works really well and stops them from smearing. I usually leave the pages/cards out for awhile til they're dry, as long as possible. It's in a spray can found in the acrylic paint section of Michael's. The first time I went looking for it I had no idea what I was looking for and took forever to find it! Hope this helps!
All the scrapping chalks I've used don't smudge but other powders and coloring products sure can. There are a million brands of fixatives on the market. Any of them should work. Krylon has at least 3 (Fixatif, Clear Acrylic Coating, Preserve It!), Creative Imaginations has Super Seal, and there are zillion others. Look in the art dept of any craft store like J's or M's or H.L., Walmart may have it in the paint section, or some good LSS may have some too. Don't worry about the brand--but make sure it's archivally safe.