So, this set of steps here misses many, if not most, of the important parts of getting a wrist lock. The most important thing missing is the connection to the other guy. You can trap my hand, grip it very hard, and step whatever direction you want... but if you have not broken my structure and taken my balance... as
@gpseymour says, there will be no pain to comply with and countering, blocking, defeating your technique will be easy. You need to connect with the other guy first. If you are connected, when you move his wrist, you will move his body and shift his weight. There are lots of ways to accomplish this off balance and structural break. Aikido and Daito Ryu are some of the best arts I have come across, that really dig into this idea.
The best way to explain this is with demonstration, being able to see and feel what is going on. But, I will attempt. If you are holding you arm out, and I grab your hand, and step inside or out side, but you have not changed your posture or position of your arm... then I will not be able to apply a lock. You are still in a strong posture and your arm/wrist/hand are all in positions of power. If instead, as I touch your hand, I put a little weight into it, this will slightly shift your posture... you will need to use your toes more to remain upright. At the same time, I slightly move your hand away from your body. You are now resisting a downwards pressure and an outwards pressure. Now, as I step in, if I maintain those two pressures, this should cause the shoulder rotations that
@gpseymour was talking of. At this point, your body is out of alignment, you are not centered in your balance, and the structure of you arm is broken. Now the lock can be applied causing pain, or injury or a take down... The trick is that if you apply this downward force or outward force too much, or too long, the other guy just takes a step and recovers. This is why many times these things are practiced from a reach or a punch... the other guy is giving you momentum, such that if you simply continue his motion a bit further, you will accomplish the structural break and off balance needed. (this is why it works in the dojo, but not on the street... the guy on the street is not giving you the right momentum. If you have never figured out how to generate this structural break, without that help, it won't work.)
The first two steps I would add to the 4 above would be:
0.0 Connect with the attacker
0.1 move the attackers weight in a direction of weakness (perpendicular to the line drawn connecting his heels, for example)
0.2 move the attackers joint out of the strength alignment
0.3 the combination of 0.1 and 0.2, should create a tension in the other guys body, even if slight... maintain this tension
Now you can start with step 1. Note that is you drop that tension or if at any point from now on, if the other guy is not moving, when you move, the technique is over. If the attacker is in a strong position, or can recover to a strong position... you will not have the leverage, through pain or any other means, to finish your lock. Also note that all the important bits happen before you think the pain starts or the damaging leverage. By applying the wrist lock correctly, it effects their entire structure, not just his wrist... thus it does not matter if they are flexible, double jointed, or not feeling pain right now. You are still able to effect their entire body, take them down and or damage them.