I also just neutralize the controls, when it gets at the right attitude, I add power and fly out upright. You need to make sure you have enough altitude especially upright. All my bigger planes just keep spinning 2-3 rev's when I end an upright flatspin. If I ever ended one of these too low it would surely spin into the ground. I believe this is what happens to most people that say they could not get it out of a spin and it continued spinning right into the ground. Eventually it will stop spinning, especially with opposite rudder and aileron. Anyway, start with lots of altitude and practice getting out. Then, when you get bored with that, you can end it the inverted flat spins with inverted harriers. Try doing upright to inverted to upright etc etc. Those are really fun, but go up nice and high.

(That face is me looking way up high at my plane).