There are a few good things you can do to help train and make the rotation more intuitive.  First, make sure you read through the "Hints And Tips" part.  This contains some helpful info which can save you time in making the same mistakes I did. 

As much difference as arc, choke, and AOR make; you will likely be paying most attention to arc and AOR with little modification to the choke.  The sections on these are mainly to help you figure out how to vary the rotation speed, especially slowing it down.  The fact is, for any useful throwing, you'll have to learn to feel what you are throwing and the rotation.  This may seem a little weird, but working this makes picking up whatever you find, throwing it, and getting it to stick accurately a lot more likely.  If you stay with mechanics, varying each thing and thinking about everything before each throw, it's not very functional. Functionality comes from being able to pick something up, feel the weight for a second, and throw. 

So, how do we train this?  The best way I've found or heard of is simply working with the rotation.  First, you'll need a large target.  Plywood or boards work well.  Boards can be nailed in line to make a decent target.  Don't use pressboard or chipboard if you can help it.  It falls apart way too easily and you'll soon have a mess.  Whatever you make, be sure to leave it so you can replace or cover holes after awhile with other wood.  Regular cut logs are ok, but we need a larger backdrop to work the rotation first before getting that accurate.  Next, you need a lawn, or at least a plot of ground.  If all you have is sand, dirt, or an extremely well kept lawn with no weeds, you'll also need some pieces of paper.  Sheet paper works fine or a cheap deck of playing cards is even better.

Check your grip on the knife.  Make sure you have enough knife so it doesn't flop around at all.  Usually a coke about to the balance point works well.  On smaller knives, a little past the balance point is sometimes good.  When you throw, bring your arm all the way back behind your head.  You will normally need to release your grip and begin letting the knife slide out before your arc gets smaller.  This means not waiting to release like you normally would with a baseball. 

Start by picking a spot such as a weed or different color in the grass.  If you choose to use cards or paper, scatter some pieces around.  The goal is to start a few feet away, throw the blades without a lot of force so you can feel the weight well, and get them to stick into or as near the target as you can.  This may seem mundane, but it will help develop a feel for the rotation of the blade and getting it to rotate differently for different distances.  Once you get a few sticks, back up some.  Go closer and further back from about five feet to fifteen feet away.  If fifteen feet feels comfortable after awhile, you can move back to about twenty.  Beyond twenty feet, it's much more difficult to get a good stick with a half rotation. 

Once you feel comfortable with this and are getting good consistent sticks, move on to the boards.  You'll need to put a little more force into it to get good sticks.  However, don't throw as hard as you can.  This can be hazardous with bounce back and tends to throw your rotation off.  Just throw moderate to start and hard, but not your hardest, later.  Start close and move back, just as you did at the ground.  If you find you are doing well then all of the sudden start messing up, go back to the ground and try to get your feel back.  I often do this when I start throwing wrong.  It helps get this feel back.  You'll eventually know a good throw as soon as it leaves your hand.  There is a certain feel and you just know it's good. 

Throw different sizes and weights of knives.  This will help with the feel and make it easier to adjust picking up something knew.  It will be harder at first because of the constant adaptation, but it will help teach you to adapt better.  You don't have to stick to knives.  Throw in a few spikes and other items.  A large set of sheers (scissors) with metal handles work well.  Just make sure that what you use is sturdy enough to take the impacts.  Folding knives are usually not and end up breaking soon.  Screwdrivers are ok but expect the handles to crack after a short time.

This is where we get into a little bit of mind over body weirdness.  One thing that will help make good throws, both with rotation and accuracy, is envisioning the throw the way it is supposed to be including the half turn and stick, just before the actual throw.  Then see it again as you throw.  After you do something many times, your body knows the feel and your mind knows what needs to happen to make your body follow through.  After awhile, you will be able skip the pre-throw envisioning and just see the throw as it happens.  This type of envisioning will help your mind control your body the way it needs to for a good throw.  The same can be applied to many physical skills to help your body do what your mind tells it to.  It sounds weird, but this really helps.

There are probably other ways of training this too.  However, this is what's seemed to work the best for me so far.  With enough practice, my guess is it could be adapted fine for full turn throws as well.  Whatever training method you use, make sure it's one that emphasizes intuitive throws using feel rather then simple mechanics.  Additionally, just have fun.  Don't worry about not picking it up right away.  Just go out and play with the sharp objects, relax, and make it fun.  Don't run with the scissors, just throw them.