Just to comment on this, there are two main traditional ways to achieve "Skeletal Freezing" in a push-hands context, and in both of them, it is the opponents who 'freeze' themselves:

One is to "join, adhere, and follow" until the opponent's body says "No" to something, at which point they 'freeze-up' and you throw them out;

The other is to cause the opponent's own attack to 'fall upon emptiness', which causes them to lose their root and balance, which causes them to 'freeze-up', and then you throw them out.

Push-hands is really not about 'doing' or 'cognizing',  so much as about 'being' in and maintaining a certain condition within your own body system; the goal is to have your 'body-mind' say "Yes" to everything your opponent throws at you, while at the same time using your relaxed but alert 'listening' energy to accurately detect the exact moment that his body-system says "No".

Practicing this way, the first person whose body says "No" to something will be the one who is thrown out  -  my teacher used to say, "Self-defense in TCC is really defense against your 'Self ', and push-hands is the training method whereby you learn this fact".

Basically, if you can learn to properly "join, adhere, and follow", your opponent will eventually over-extend his energy, or his body-system will absolutely refuse to accept a certain type of energy from you along a certain 'return' vector, and then  -  he's out of there.

PS: I thought some of you might be amused by my teacher's definition of "join, adhere, and follow":

• "Join"  =  "Do not oppose" -  when you 'join' an organization, you do not simultaneously 'oppose' that organization; the body-feeling is : "Oh, we're all going 'this' way", and you whole-heartedly go along.
• "Adhere"  =  No 'Butting', which means using too much pressure, which may 'wake up' your opponent and cause him to 'change'; and no 'Thin-ness', where your connection is too weak for you to accurately follow or neutralize your opponent's energy  -  either 'Butting' or 'Thin-ness' also interferes with your own ability to 'listen' properly.But the essential feeling is that he doesn't feel 'threatened' or as if he's not still 'in charge' of what's going on -  he should always feel as if he's the 'Actor', and you are merely the 'Re-actor'.
• "Follow"  =  Continuing to apply 'join' and 'adhere' while your opponent travels through a series of 'changes'; when his body-system overextends too far and his balance is compromised, or his body-system says "No" to some form of energy that is 'returned' to him, he will 'stop' himself (or '"freeze-up" , if you prefer), and that's when you issue fa-jin and toss him out.

The words "stick, adhere, and follow", mean the same thing as the descriptions I passed on for "join, adhere, and follow", wherein "join" is substituted for "stick".

I have seen many really good Chinese teachers use these words almost interchangeably  -  that is, 'join' meaning the same thing as 'stick'; the words 'adhere' and 'follow' seem to be used generally in the same sense that I described them.

I was also really interested in getting these statements out there:  

"Self-defense in TCC is really defense against your 'Self ', and push-hands is the training method whereby you learn this fact".

And: "Push-hands is really not about 'doing' or 'cognizing',  so much as about 'being' in and maintaining a certain condition within your own body system; the goal is to have your 'body-mind' say "Yes" to everything your opponent throws at you, while at the same time using your relaxed but alert 'listening' energy to accurately detect the exact moment that his body-system says "No".

Also, practiced in this way, the 'attitudes' and reactions programmed into the body-system in push-hands can easily be carried over into free-fighting.