I think Cortec is a great product. I thin mine with lacquer thinner and keep a small quantity mixed up in a plastic container for daily use. The lacquer thinner helps it to dry quickly. I apply it with a sponge. I usually take a regular kitchen sponge and slice a 1 inch wide strip. I dip it in the cortec and slide it along the area to be protected. That is probably the same as you are doing with the sponge brush. I only protect the surfaces that mate against another surface.
You may be putting the Cortec on too thick. I have just a thin coating of the Cortec on the surfaces I am mating.
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