You are planning to learn to move a difficult and valuable(?) piece (for your first attempt?) and I think this undertaking has the potential for disaster. However if it is that or dispose of it....
There is a plan here for a cheaply made piano skid, but be warned! - It may not be suitable for your needs since you have not given the dimensions of the piano.
A Kidney shaped piano is turned over the opposite way to a piano with a straight edge, to rest on the 2 'lobes of the kidney, rather than the curved side.
It will be important that the piano does not overhang the skid and that plenty of padding is
used. I would remove the lid since weight applied on the hinges could tear them from the body.
Also in your case I would consider ratchet straps lightly applied, if you are not used to tensioning professional moving straps.
