I recently purchased General's pastel chalk pencils. They work great on all fabrics and have a pencil sharpener inside the box. I also use the wash out blue markers sold at Walmart (Mark B Gone). They last longer than other brands. I did have a problem with some marks not coming out of my last quilt, but I will try soaking it again in the washer. I will also try soap slivers. Sounds like a great idea.
Does anyone else find it hard to hand quilt through fusible batting?