Locate the exposed sewn seam along the edge of the cushion. It should appear as if part of the edging is sticking out on about 4 to 6 inches of its length. Carefully cut the exposed seam using a seam ripper. Do not cut the cushion fabric as you cut the seam.
Remove the old infill from inside of the cushion. If the cushion had cinched buttons, be careful not to rip or tear the stitching. Dispose of the old infill.
Insert new infill into the cushion through the opened seam. Select either cotton or polyester infill, which are non-allergenic. Insert the end of a 1/2-inch diameter wooden dowel to push the infill into the corners of the cushion. Fill the cushion as full as you prefer.
Pinch the opened seam back together, lining up the edges, and insert straight pins along the seam to secure it in place.
Sew along the pinned edge using a sewing needle and nylon thread, then cut off any excess thread before using the cushion.
Repeat to fill as many cushions as you require.