I swear, I have tried everything. He's my experience, for what it's worth.
When it works, pounce chalk is my current favourite. But I find it doesn't work well on heavily pieced items (like a watercolour quilt with 1" squares). And doesn't show on light fabrics. The blue pounce requires water to remove, so I haven't tried that.
I used quilter's pencils, and had a heck of a time getting the marks out (took 2 washings). I know I was pressing too hard, but I was not overly impressed - neither with how quickly I went through one pencial, trying to keep a sharp point. I some mechanical pencils (white and dark) which I haven't tried yet, so that's next.
Chalk comes off soooo easily - but it is currently my second choice marker, after pounce (or if I'm not using a stencil). I had a set of coloured chalk pencils in hand one day (I swear I've bought pretty much every type of marking tool my quilting store carries). But the store owner told me not to use it. Esp. the yellow, because it doesn't come out. So I put that one back and didn't tempt fate.
The blue water soluble works really well. And I have found that I can remove the marks simply by lightly blotting the quilt with a damp cloth (heavier blotting required if my marks are dark).
I have used the frixon pens. So far no issues, but since it requires a wash to fully remove, I'm reluctant to use. I've also read of some issues with them discolouring very dark fabrics.
I bought a white/invisible marker for darks. I hate it. The lines don't show - they supposedly get darker as it dries, but I still couldn't see the marks on my blacks.
I have disappearing ink pen - I think it is great, but disappears SO fast. I used it for handquilting, marked just a few inches at a time (I was echo quilting). And I use it for quick marking like mark & sew a diagonal across 2 squares for HST. But could never mark a quilt with it for machine quilting, because the marks would fade.
All my troubles lead me to believe that true free-motion - unmarked - is the way to go for quilting. But I'm not that brave (yet)
