Strictly speaking crosstalk was fixed in P5, and no longer happens in later versions. What is referred to these days as "crosstalk" would probably be better described as "targeted slaving", but I'm being pedantic, call it crosstalk if you like.

Normal slaving code uses numbers to tell Poser which figure the slaving refers to, eg:

            valueOpDeltaAdd
                Figure 1
                BODY:1
                One
            deltaAddDelta -1.000000

I have highlighted the numbers in green. When a poser figure is loaded, Poser will update the numbers in the above code as appropriate. So it there are already two figures in the scene when you load the above next figure the slaving code will become:

            valueOpDeltaAdd
                Figure 3
                BODY:3
                One
            deltaAddDelta -1.000000

If you leave the numbers out of the slaving code, Poser will use the number from the figure that was selected at the time the new figure was loaded, and this is what you want for "targeted slaving", also known as super-conforming or crosstalk.

So the answer to the question "But how do I get Poser to cross-talk morphs between conforming clothes and the character?" is that you leave the numbers out of the slaving code in the cr2, so the code looks like below.

            valueOpDeltaAdd
                Figure
                BODY
                One
            deltaAddDelta -1.000000