Attach an output to your input, say output 3/4. That's your reamp signal. Record that output to a separate track. Assign the output of that track in your DAW to another output like 5/6 and feed that output, in parallel, into your grid. Unmute the reamp track in your DAW and it'll run the reamp signal through your signal chain and you can capture it via output 1/2 back in your DAW.How do you do it? Set one of the outputs to be dry?
You can even do analog re-amping with the II. With the II you can't monitor the rest of your project while re-amping. But otherwise it can be done.