Why do you need to dehydrate your sections for fluorescence microscopy? I recommend that just mount them with a brush on glass that has a drop of your mounting medium, orientate the section, and put a coverslip on top. Seal around with a the coverslip with nail polish, once the nail polished dried you are ready to microscopy. That is what I regularly do and it is successful with brain slices or cultured cells. For an example see my publication below.
best wishes, Refik
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