OK, a FLAT SPIN: I do them occasionally and here's what works for me. Hopefully someone else will enhance this initial input (thats Man-talk for correcting me!).
Zeroth step: check all hinges and linkages on your ele, aile, and rudder at full throw to make sure there's nothing binding, loose or broken. Flat spins are a tad violent and tend to test your hardware.
First, a spin is tricky because you have to stall one wing (inner) while you still fly with the other. You essentially fly around the stalled wing, ideally I think you pivot at half the span of the inside wing.
Make it a bit tailheavy- that helps get it into the spin. This also helps it to stay in the spin, most planes I see flat spinning well are naturally a bit nose high. I personally can't spin if it isn't tailheavy.
Have a lot of elevator throw, like 40+ degrees, on your high rates switch. Set your rudder to at least 40 degrees, too.
Set your idle a bit high- stunting tends to foam the fuel and cause deadsticks without a high idle. You also will idle for most of the spin- so the high idle helps prevent loading up.
You need your engine at the end of a spin to get out sometimes, so hi idle (=live-stick)is good. Many of my buds set an "idle up" switch and flick it on for stunts like flat spins.
Now grab a gallon of fuel- it will probably take that much to get your first good spin or two. Took me 2 gallons but I'm a heavy drinker!!
Climb waaay up. Higher than the three mistakes high that instructors want where you can barely see what its doing. That buys you some time to jack around getting it into the spin. At the end of the climb, you are ready to spin. Level out, pull back on power to idle, and keep increasing elevator to hold it level (in pitch) as it slows down, but not so much that it porpoises. When it porpoises both wings are stalling.. that's too slow.
Now watch the plane.... it will eventually choose a side/direction to drop toward as the plane slows toward a stop with what is probably full up elevator by now- throw the rudder in that direction while still holding the up elevator. The wing that drops has stalled...and now you are using the rudder to rotate around that stalled wing.
Once the plane starts rotating, you can work the ailerons to either go with the rudder direction, essentially pushing it to roll inward heading toward a nose down roll, or pushe the ailerons opposite the rudder, countering the tendency to roll in and holding it flat. Obviously the goal is to keep the plane flat, and on this Extra usually that means using opposite aileron- but not at first, in my experience.
I usually have to go ailerons with the rudder a bit to initiate the spin, and tighten it up a bit (spinning faster)- then go the other way with aileron, about half throw, to flatten it out, and 1/4 opposite aileron keep it flat. Each plane will be different, depending on incidence, CG, throws and weight.
This is not a "jam the sticks in the corners" manouver, you have to work with it as the spin develops. Just keep trying and trying until it suddenly cooperates.... then it may take another 10 tries to get it to do "THAT" again, but stick with it. Its worth the trouble.

Remember to watch your ALTITUDE... start high and have a buddy watching where the ground is. You exit the (upright) spin by relaxing the controls back to neutral and adding some power if you are at or near idle. If that doesn't do it, Use down elevator to point the nose at the ground and count to 3. This gets you back to flying speed and all is back to normal controls wise. Start nice and high, as the all important exit takes a good 50-100 feet and needs to finish before your altitude reaches zero.... you'd be amazed how many planes pancake in while the pilot is saying "check out that flat spin I got it to do"!!! Sometimes the plane almost acts like you are having radio trouble as you exit the spin... because you have stopped flying at that point. Leave lots of room for spin recovery at first.

On this particular plane, I find that I usually have more down than up elevator, and therefore it prefers to enter & hold the flat spin inverted. If you try inverted flat spins, you will have to reverse elevator and aileron inputs, if you think about it. For instance, you will use DOWN elevator to enter the spin and probably go ailerons opposite the rudder at first, then ailerons with rudder 1/2- 1/4 throw as the spin develops & then at the end you may need UP elevator to get the nose down to exit the spin. I know its a bit confusing, but a real blast when you get the hang of it.

After your first gallon or so of near-flat spinning, when you know how to enter and exit the spin and its a bit routine if not polished, you might try adding some power, say 1/4-1/2 throttle, (while maintaining the full rudder throw). This will sometimes help to "flatten out" the spin, i.e. slowing the rate of descent while it is spinning = more joy time.
Inverted, where mine likes to spin best, I can actually get it to hold altitude and occasionally climb while in flat spin.... my particular build needs full throttle for that.
Most planes have a preferred direction for flat spinning, where they enter and maintain the spin better, and the myriad of variables that set that direction mean its a try-it-and-see proposition.
I would guess that a right rudder upright flat spin is most commonly easier on these , because of the built in right thrust of the firewall and 2 degrees right fin setting.
whew, sorry it took so long- lots to tell there! Have fun, wheels down!