I started a thread about this several months ago. The major issue with this problem is that there is no secure way to communicate the "secret handshake" without preventing the enemy from also getting to know about it. So the enemy could easily get to know the secret handshake and use it to sniff out apostates.
I think the solution to this problem is to not use a specific, fixed, "secret handshake" that is shared publicly. Instead, you need to share publicly only a vague protocol, which, in turn is tailored by each individual to produce their own unique "secret handshake" that is never to be shared publicly on any forum. This way, the enemy does not have any specific "secret handshake" to look for. They would only know of the vague protocol. Of course this doesn't solve the problem. It is only the first step of the solution which makes it more difficult for the enemy.
The second step of the solution is to use have a full proof backup plan to extricate yourself from incrimination if you've being baited by the enemy. You have to design your "secret handshake" with this in mind.
One possible solution I came up with is a protocol where you ask the JW an edgy question that has a TTATT meaning along with a plausible innocent meaning. It would be a good idea to have multiple such questions in mind; and never share them publicly online. If the JW is awake he responds by answering with an edgy answer that has a TTATT meaning and a plausible innocent meaning. This way you make it known to each other that you are awake (by the TTATT meaning) while simultaneously giving yourself a way to extricate yourself from incrimination (by claiming the innocent meaning) if you've been baited by the enemy.
You use multiple such questions and answers to establish trust and certainty that the other person is awake.