your plane should be fine, and yes, use full 3d rates, preferably 45 degrees all around, maybe less on ailerons...

there are two ways to enter, from a stall after cutting power in a vertical climb, or by starting into a downard spiral and leveling out....

the stall is an easier entry, but you have to know where your plane likes the sticks for a good flatspin... I usually cut throttle, feed in rudder just as it falls back, then elevator, and continually feed in a little bit of aileron until it flattens out (imagine yourself in the plane, if you are spinning to the left, you use right aileron, naturally the plane will try to dip the inside wing, use the aileron to counteract it and flatten out, but don't over-do it, or the plane will flop out....

the other way, is to start with full rudder and elevator, but start with opposite aileron of what you would normally use in the flatspin, the plane should spiral down pretty fast, once it gets going, push the aileron the other way and flatten out

keep it a few mistakes high the first time