I think the frog kick can be hard to learn by yourself. And it can be hard to learn with the wrong fins. When I took Fundies, I was using soft paddle fins, and I was doing the kick completely BACKWARDS. It took having my instructor behind me, turning my ankles in the proper direction, to allow me to "get" the kick.
My best advice would be to hook up with an instructor who can teach this, or a mentoring diver who's able to watch what you are doing and see if it's correct. I don't know where you are in Maryland, but if you're near DC, you might PM cmalinowski here on SB, and see if either you two can get together for some practice, or if he knows of an instructor to recommend to you.