Steve,

I can see by wording in your question that you already understand the
cross-talk which will be derived from the common primary source
antibodies. Therefore, a trick we use when we have to do this is to
complete the entire first labeling sequence then fix the tissue with 4%
PF.  The second sequence then begins with a quenching step to remove the
excess fixative followed by a complete labeling sequence for the second
primary.  We run a parallel sample reversing the order of the primary to
verify the localization.  I will add that this does not always turnout
the way we would like, but it does work.

Regards,

Skip