One of the biggest flaws in morphs is image pixelation caused when enlarging something. My method makes the final image smaller to minimize this tell-tale sign of a morph (See my Tutorial, Section 2, 4th bullet). Unfortunately this doesn't eliminate pixelation completely. Here's a few steps to hide this flaw even more.
Unsharp Mask: After an image has been Warped, Distorted or (Lord help me) Liquified, the selected image becomes slightly blurred. Use Filter>Sharpen>UnSharp Mask to bring back it's crispness. You can play with the settings for best results, but I start at Amount–50%, Radius–.05 & Threshold–1 and go from there.
Sharpen Tool: On the side toolbar, there is a raindrop type shape or Blur Tool. Click and hold to bring out the submenus for the triangle shape or Sharpen Tool. You can adjust the size and strength of the brush to sharpen any specific area of your choosing.
Clean those edges: When major warping or bending of an image occurs (REALLY BIG muscles or breasts), no amount of sharpening will help the outside edges from pixelation. It's best to go back with the eraser tool using a hard edge setting to clean it up. For a smoother shape, re-outline the desired area just slightly inside the edge and erase the unwanted pixels.
See the Full Tutorial and Happy Morphing