Yes, it is a little tricky. Just as with a straight bow, you want the whole limb to bend evenly. That means each part does an equal amount of work. But that means it won't LOOK even. The deflexed part near the riser will look like it's bending too much, and the outter limb where the reflex part is will just straighten out.
Some people interpret this to mean the outter part is supposed to be stiff, and all the bending is supposed to happen in the inner limbs. Then, they make the mistake of making the outter limbs not bend much at all, while the inner limbs do all the work. Then their bow breaks, and they wonder why.
The opposite mistake, of course, is treating it as if it were straight and getting a nice D-shaped arc when you tiller it. If that happens, it means your outter limbs are bending too much, and your inner limbs aren't doing their share of the work.
There's a couple of ways to get a feel for how it should look. One way is to look at a reflex/deflex fiberglass bow and notice how it looks when it's unstung, when it's strung, and when it's pulled all the way back.
Another way is to just watch the limbs flexing from a distance so you can actually see the limbs bending in motion. A tiller tree is good for that because you just stand away from it and pull a cord.