If it was me, I would "feather-edge" any dry spots, then go over the whole back with a medium grit paper (by hand w/ little pressure). That gives the "primer" some "tooth" to give even and excellent adhesion.
rich
Stix....maybe you could post up a pic or two and I'd bet somebody could get ya on the right track sir. Seems like we got a whole bunch of talented guys floatin around.
rich