If you are worried about Tween 20 being left on your IFA sections, why not
do a final rinse using pure PBS without the Tween 20. 

I've always coverslipped my IFA sections, I'm not sure about stability of
uncoverslipped sections over time, even days.  There are liquid coverslips
ie Crystal mount which is supposed to work with IFA's even in large batches
of slides.  

 
 
Gayle Callis
MT,HT,HTL(ASCP)
Research Histopathology Supervisor
Veterinary Molecular Biology - Marsh Lab
Montana State University - Bozeman
19th and Lincoln St
Bozeman MT 59717-3610

406 994-6367 (voice mail)
406 994-4303 (FAX)

email: UVSGC@montana.edu