I, too, have been there with what to use to mark the quilts. I've not had much success with the stuff I've tried, but being a total newbie, it may have been my fault. Blue pens work great as long as you can see them and remember not to ever iron over them as that makes them permanent or semi-permanent. I tried soapstone, but it was hard to see. Chalk worked great on dark fabric, but the point gets dull quickly and it's a pain to sharpen. Mechanical pencils (the normal kind) work great but you've gotta wash the quilt when you're done.
I ordered some Frixion pens from JetPens and managed to add enough stuff to get free shipping. (They were fast to ship, btw.) I ordered some lighter colors to try out on the next projects, a group of lap quilts for a nursing home that my quilting group is doing as a service project. My local Staples also has them in either black or a trio of black, red and blue. The Frixion pens come in a lot of colors, just not white.
I've read a lot of comments from people concerned that the Frixion pens ink reappears when the quilt is at or below about 14 degrees. Personally, if it's that cold, reappearing lines on my quilt is not something about which I will be worried at that time. I'll be worrying about keeping my tush warm and the water pipes not being frozen! :lol:
BTW, I played with the Frixion pens a few weeks ago just for kicks during our last heat wave. The lines will start to disappear when the heat index hits triple digits. Just giving a heads up.
Good luck!
M&M