Polyclonal antiserum in whole mount

[Vayuputra]

I have obtained some polyclonal (from rabbit) antiserum against a 
fusion protein I generated; this antiserum works quite well on western 
blots.  I was wondering if anyone has suggestions for getting optimal 
results using the same antiserum in whole mount 
immunohistochemistry on 18-36h fish embryos.  I tried it once without 
any success.  I would greatly appreciate it if anyone can give me some 
pointers.  

Thanks.
vAyuputra