Lot depends on rearward CG and enough rudder and elevator movement. I have a 4*60 (slimy glow) that flat spins like crazy. I start by shoving both sticks up and left. Then as spin begins, slowly cross airelons by moving right stick to right top. Keep throttle all the way open and the thing flattens out and spins very fast. Of course starting high and allowing for the wind is important. Also have a Goldberg Ultimate that spins like crazy. Both planes have CG set at rear most point and have lots of throw in tail group.

Now flying a GP Reactor but have not tried spins yet--still working out battery issues.