Funny I should be snooping on this thread. I am currently working on some blocks that I used the clover marking pens that you mark on fabric with and they still washed out when I put water to them to see if I should finish them. This is what I would use or there is one out by Zip that works nicely as well I use on my quilt marking. This is what I do. there is not reason you can't and I am with you, just in case I don't hit the line perfectly this takes away the scare of it showing.