Holice, I think listing steps is important.
*Prewash all fabric (unless I cant.....at a retreat....just had to have....from the vendor....use it now!)
*Press usually dry iron, not spray. Sometimes use water spritz or steam. Do NOT use Best Press or Starch, etc.
*Mark before assembling sandwich. Blue water erase pen preferred. White, pink or grey ceramic lead second choice. Frixion third choice.
*For water soluble pens/pencils, soak in warm water tub for 1/2 hour. Squeeze out water. Lay out flat to block.
*For heat removable products, press with iron, then block.
Have never had a problem with these methods.
Did have a quilt marked with blue water soluble pen. Gave it lots of water spritz, layed to dry, it came back. Was pretty careful, but did iron some of the returned marks. Then tub soaked it....it all came out.
Light color fabric is easy to mark. Highly patterned with lots of value contrast and dark fabrics are a challenge. For dark fabrics the ceramic pencils are the only I've found to show up. For highly patterned I've quilted it using an ebroidery machine, FMQ or panto...no markers have given a visable line I can follow.
Have gotton crayola water soluble markers and pounce powder that doesn't blow off. Haven't had chance to try them yet.
This is a subject I still watch for at international quilt shows, what product is out there now?