anthter way to do this is to have your pattern on your muslin...go dig out all those parts of broken crayons, half ones, etc. then peel off the paper, drop the crayons by color into an old muffin tin, set it in an electric skillet that has water in it(and the skillet is on and hot!)....the crayons will melt quick and once they have, actually 'paint' the crayon thick where you want it. I tape my fabric on an old newspaper to hold it in place. This is fun!! Once your pattern is done, then put that piece of crayoned fabric between newspapers...iron. You will need to have extra papers on hand to keep melting. You will have a great time w/this!
For those wanting to batik theirs....You can also do this, and when the crayon is dry on the fabric.....when project is finished w/the crayon painting...wad it up, straighten, and do this again. Then place colored fabric back on newprint...and, using a paint brush, paint ink (can pick up at hobby lobby in jars)across the whole picture. It will run between the cracks, even if it isn't real visible. When you iron as above...you will have your homemade batik!:0)
Make sure your crayons are the 'safe' crayons for the little ones. I always stick w/crayola. Just some tidbits....Skeat