I Need A Marker That Won't Drive Me Crazy

Here's the good news--I finished quilting and binding the Disappearing Nine Patch quilt that I'm calling Cobblestones.

It's to go in a fundraising basket for my grandkids' school, and was due in February, so I wanted to get it done in plenty of time.

This is the quilt laid out on the floor.  I quilted a 6 in. grid in the ditch, and then added diagonal lines through the squares.

The back is a swirly tan/beige leaf print.
Quilting in the ditch was E-A-S-Y.  Then I had to mark the diagonal lines.  Ack!
Does anybody out there still mark quilting lines?  If so, what do you use?

These are the choices I have in my sewing room--white pencils, white chalk, silver pencil, hera marker, soap, and regular pencil.  Each one drives me crazy in its own way.

My requirements are pretty simple. 
1.  I must be able to see the marking while quilting. (Duh.)
2.  The marks must come off completely after quilting, but not BEFORE quilting. (again, duh)
3.  I don't want to mess around with chemicals that won't come off if they get hot or cold or whatever.

I have been wrestling with this problem for 40 years.  I love quilting in the ditch or with the edge of the presser foot, since no marking is required, but sadly that doesn't work for everything.

If anybody can give me a hint or a suggestion, I would be absolutely thrilled.
In the meantime, I've got an earworm of John Cougar Mellencamp to deal with.  Sorry if I gave you one too.
Have a wonderful wintry week!
Cheers,
Sylvia@Treadlestitches

Linking up with Crazy Mom Quilts and  Busy Hands Quilts.