I use all kinds of different things in my dog beds. What you do with a lot of scraps that are small put them in the envelope and move them around till they are even, then stitch like you are quilting through all the layers, takes only a few minutes and even if that may blog it is only in small areas that doesn't bother the dog. I have used socks too, I cut the socks in half, flattened them as well as possible and sewed them down to the back then made the sandwich and turned inside out and then do some stitiching, like quilting. Not hard and they wash up nicely. You can use just about anything that you can wash for dog beds. It is best to use a heavier fabric or a touch fabric on the outside but a washable one. Dog blankets I will use regular quilt fabric, usually what I call ugly and line it with an old sheet or old flannel sheet, old blanket, etc. Do the same like an envelope. I always put some quilting in everything to keep the back and front together.
When I sew I throw everything into a bag, thread bits and pieces, every thing I can't use to quilt with, then sort when I get a bag full. Then make dog beds. You can actually save up enough threads and small strips of fabric to stuff a cat pillow or something like that, as well.