These things rock!
There's a little learning curve, but after doing a few pairs you get the hang of which way the clips need to go into the plastic housings, and which side should be red, so that it matches up with RIGrunners and other ham stuff. Check the orientation several times before crimping at first, especially when using zip cord, where the two conductors are joined together, because if the two clips get crimped with more than about 30 degrees of twist between the two it may not be possible to seat them both in the housing. Been there, done that, that's how you learn.
My method is to hold the pair of wires side by side with the stripped ends pointing away from me in my left hand, with the red wire to the right of the black. Starting with the red, insert the stripped wire into the barrel of connector making sure to keep the blade flat, with the distal end of the curve pointing down. Maintaining that orientation, slip the connector into the appropriate third of the crimp die and gently squeeze.
The 30s are the easiest because they have a complete barrel that isn't as finicky to keep aligned, plus the optimal gauge wire for this size is stiff enough that it slides right into the housing and have enough insulation to provide adequate strain relief for the connectors. The 15s and 45s are necessary for the thick and thin stuff, but often require extra care to install.