Do I have to pre-wash wrap-n-zap before using it?
Are you referring to a specific project you saw here on Hometalk?
Yes Bowl cozies
Here is one video with instructions on how to make the bowl cozies.
The fabric is not pre-shrunk. Instructions say to use 100% cotton interfacing, and 100% cotton fabric.
However, to ensure that the pellon interfacing and the fabric do not shrink more than the thread, use 100% cotton thread as well.
Thanks whats the best way for care instructions to put in when giving them to people?
Wash in warm water on delicate or gentle cycle in automatic washer, in a netting 'lingerie' bag. Or, hand wash using gentle squeezing motion, not twisiting or wringing.
Do not dry in automatic washer, as the heat will cause shrinking and bunching up of the pellon interfacing.
Air drying over an upside down bowl, and hand blocking during drying will help the cozy keep its shape.
Once dry, spraying with Scotchguard spray will help keep the fabric stain and moisture resistant.