Couch cushions rehab- Whats the best way to refill?

Remove the covers from cushions. You should have foam wrapped in batting. It may also be encased in a fabric type pillow case. Check to be sure that the foam is in good condition. Your problem is more likely the batting that tends to shift around and gets 'lumpy' for obvious reasons. You may have to cut or rip a seam but you need to remove the 'pillow case' to replace the batting and/or the foam. If it's the batting, replace with new batting. I would over wrap the foam , meaning that I would use twice as much batting as was originally. This way the batting won't shift nearly as much. Replace the pillow case. Hand sew the seam that you made to remove the foam and batting and slip cushion cover back on. The extra batting will make this a tight fit but it will be worth it in the long run. Any good fabric store (Joann's) will have wide widths of batting, (normally used for quilting) that will do the job nicely.

Do you have a commercial grade foam store available? If so, go there with your old cushions and you can have new ones cut to fit. If not, a fabric, craft or hobby store will also have foam, but you need to cut yourself with an electric knife. You can also just stuff in extra cushioning - fiberfill or quilt batting to fluff them up again.

If you have to replace foam , be prepared to pay the price. Very expensive! I purchased a slab 5' x 18" x 3" and the cost was around $80. Wish I'd known at the time that the quality of the foam is inferior to what a wholesaler stocks. Disappointed!