I love finding batting bits at the thrift shop and buy them. They are often in long strips which have been cut off the edges of a finished project. I use iron on interfacing which I cut with my rotary cutter a couple of inches wide and press them onto butted together edges of the batting. Cover first with pressing cloth or it will melt. I have made Quilt as you go blocks and made them into quilts also. When they are finished no one can tell if they were the same batting or not. I try to use similar thickness throughout the quilt.
Be careful of making pot holders from batting unless it is all cotton. Other batts melt easily and burns happen..trust me..I know from experience.