Consider doing this in the Library. You will need a toy hammer. Choose a trash weapon and transmogrify it in Halls while being hit by Jester's missile. Then, go to the quick-travel room, choose the top-right door, then go to the right (there will be a shop). From there, go up. You will find some ghost armors. Kill the first one to clear the way. Lure the second ghost armor to the edge then jump-hit it from the lower level. Decrease its health with regular weapons then continue to jump-hit it with a toy hammer. This will require some time. If the armor drops down, lure it back to the upper level, then return and continue the process. When you need to heal, go downstairs to do it. If you have accidently killed the ghost armor, restart and try again.