I guess 3DPaint tool would help to paint those seams, but in general Maya is not so good at this area, so You may wish to use Bodypaint3D or something else 3d-party-kind/standalone.
and basically it depends on what kind of texture You want to un-seam.. You could project a piece of texture on whole mesh and then erase unneccessary areas and smoothly blend with original in Photoshop. solution could change from case to case.