I have not heard of using batting scraps as fire starters but they should work well with the wax and egg carton.
I am going to do a I Spy with 5 inch batting squares and 1 inch black sashing. The sashing will finish at 1/2 inch and the batting edges at 1/4 inch seam will fill the sashing. I will quilt the squares as I go and then add a backing to the whole front and then stitch down the centre of the sashing. I hope it works well and should use up a lot of my smaller batting pieces.