To begin your prep work, first get your piano ready:
Move your piano downstairs and outside after making your nice neighbors haul it up two flights of stairs a couple months ago.
Remove the "music desk" on your piano (this holds the sheet music).
Remove any hardware, like the pulls for your lid.
Next, you'll tape everything off, sand, and then dust.
*For an amazingly smooth and lovely piano finish, don't ditch a good prep job. This includes taping, sanding, dusting, and priming. I know some tutorials ditch sanding as prep work at times, but I sand because I care :) It also creates an unbeatable smooth finish.
Using the brown craft paper and painter's tape, tape off and cover anywhere dust can get into, or anywhere you don't want painted. This includes:
Inside the top of the piano
Covering the piano keys
Covering the piano foot pedals
Covering the metal hardware for the music desk
Remind yourself that any color is better than a beat up color, and then begin to sand with 60 grit sandpaper. You don't need to sand until the brown finish is off. Just do a nice sanding over the whole piano. Sanding is used for two main reasons here, to (1) help the paint adhere better to the piano and (2) create an ultra smooth finish.
Wipe off most of the dust created by the sander initially with a dry rag, then use tack cloth to wipe the rest off. Using a tack cloth makes the finish super smooth and bump free. Wipe until it's smooth and without dust.