Swamps gave good advice. Also, when I finish and line it up from layer 2 over the original layer, I put on a temporary 50% opacity so I can be sure it’s perfect, then I turn off the opacity. Also, depending on what the subject matter is, I put a soft layer drop shadow on it which can help blend it a bit. Then make a “save as web” so that you can see it in preview and not accidentally flatten your psd file. You can see something I just did this to at YouTube by searching tiger woods roaring success radio hour.
I don’t use “save for web” It overcompresses the file. On the stuff I like I save a large Tiff file 2700 pixels wide and a JPG 800 pixels wide for sharing. On the 800 wide stuff I end up with a file about 200kb. I’ve been donating prints to a wildlife rescue center and the local humane society so I want a good strong file to send to the printer.