Bubble wrap wrapping on the part, then in a heavy-duty cardboard box, with all the voids filled with more bubble wrap. L-O-T-S of bubble wrap.
If you cant get a thick enough cardboard, double the walls with sheets of cardboard from other large boxes.
Seal all the edges shut, things can leak in shipping. Nasty things.
Use USPS as often as you can. Their rates are competitive, and they seem more able to not destroy your shipped item. I call UPS naughty names when I'm alone; they can destroy anything.
Oh, and if you have to ship to Canada avoid UPS completely: they have redonk-yew-lus "brokering" charges over the border. If your buyer wants to use them, warn them!
You shouldn't be ashamed of advising your buyer of large items that he (or she) will have to pay for the packing materials needed to give their item a chance to make it there in one piece, and bubble wrap is not cheap.