Yeah that's one of the advantages of gluing a backing. If you are strictly adding reflex, you can just block up the tips and secure down the middle of the handle. I've seen some people suspend the bow between 2 saw horses and hang a gallon jug of water from the middle. There's a few ways to do it, and a caul isn't necessary. If you floor tiller it before glue up it should bend nicely.
Before glue up I check the thickness with a caliper every 4" or so down the limb, and make sure that it is tapered properly. Then I bend it on floor and ensure that both limbs are bending the same, and make sure it's not too thick. I grab one of my finished bows that's similar in weight to compare limb strength to see if I'm close.
I guess the experienced guys skip the caliper step and they know if it's too thick by floor tillering, but it works for me.