It would help if I could see your image, but anyway...
Various clean-up techniques:
1) Filter > Dust and Scratches... (increase the pixel value depending on the preview result)
2) Blur > Gaussian Blur (ditto)
3) After either of the above, experiment with Sharpen > Unsharp Mask (to make a blurred image crisper)
4) The brilliant Rubber Stamp tool. With this, you "sample" an area of desirable image (in your case, the non-grey areas), and paint this over the undesirable bits. Especially useful for touching up imperfect models, eradicating cellulite, hairs, scars, bruises, blemishes, etc.
5) The Blur tool - manually blur areas of the image.
6) The eraser tool - erase annoying bits of the image. Very yseful also for creating transparency for GIFs, but beware - your picture MUST be a "layer", not a "background" for transparency, otherwise you'll just erase to your background color. Create a layer from a background by double-clicking on the padlock symbol in the layers palette, and "naming" the layer. If it's already a GIF, go to Image > Image Mode > RGB color (as opposed to Index).
Keep asking, enjoy the best programme in the universe, and forgive the delay - I had meningitis this weekend, and am still reeling from the humiliation...