I have done more than a few snippet projects over the years.
You have the concept correct . Apply the fusible to the fabrics. Remove the backing from the fusible. Cut small ( typically no more than 1/4 inch wide) little peices /strips and layer the colors/shades to create the image.
It is best to not to create a bowl of pre -sniped colors. Getting them flipped to the proper side .. is a major pain! When working with a color Snip directly over ( about 1 inch away) or where you want that color to be.
Layer and vary the colors/shades to get more depth. Smaller snips work better than larger.
I do take may fabric and make a pencil outline of the image I am trying to create as my map. You can also add elements by using a teflon sheet. this allows you to create a whole component image seperate, that way you can fuss with it not on the final work piece.
Tip you may want to get some images from coloring books and reduce/enlarge to help guide your process. Making a chick may sound easier than it actually is. Use these images the double check your scale and placement before using the good stuff.