The best advice that I can give, and I do this to both freshly killed meat and to meat that's been in the freezer for a couple months, is to do an ice-water bath right before tossing them in breading.
I get a cereal bowl-sized bowl full of cold water, put ice cubes in it, and dump a bit of salt in it to help melt the ice/make the water extra cold. I rinse the filets in the ice-water bath for a good 10-15 seconds. Pull the filets out, let the excess water drip off over the bowl, and throw them straight into my ziploc bag of breading to be tossed around
This really helps to firm the meat up and make it good and fluffy. Give it a shot and let me know what ya think