Not quite sure what you mean with the shader. You can do it in PS by painfully going to the last 2 pixel rows and painting a solid color

but If you buy the DVD for GI texturing which I did for SM, it will tell all that Maya can do with seams. If not PM me and I may let you into secret of a well hidden tool that seems (pun not intended) to go un- noticed alot

Cheers
Jay