Here you can see how we first layered parchment paper over the entire painting. We attached them together with staples using hospital corners, so that nothing was actually affixed to the painting itself. (you can see the note I tied to the stretcher bar, for the new owner) I like parchment paper best because there is no worry about wax or paper residue accidentally sticking to the painting. I just need to find a cheap source for larger sheets!
We then layered the front and the back of the painting with a flat sheet of corrugated cardboard. Another layer used blueboard insulation. Its light, cheap, and very sturdy - its also used as modeling base for model railroad builders and ball joint doll makers!
We taped those three layers together with regular box tape and then cut up an unbroken box, and used its corners to protect the entire new bundle. Corners can be the most vulnerable part of a painting in transit.
We procured a very large mirror box from Pier 1, and placed the whole bundle into it, stuffing large quantities of crumpled newspaper around it. I'm sure we could have used lighter packing material, but this was what we had on hand that day - and it was free! (I painted out the printed info on the box, to minimize any shipping confusion)
We then dropped it off with Fed Ex Ground and sent it on its way. I'm glad to report that it arrived safe and sound. :)
If anyone wants to chime in with their packing tips and tricks, I'd love to hear them!