Recording with a Reamp device is easy if you connect your audio gear up correctly.
Here is a way to record a great sounding dry or clean signal while monitoring and recording your favorite amp and speaker combo with a microphone.
After you are done you can use the dry signal and a similar signal patching to Reamp or re-record the guitar parts while tweaking your tone, layering effects, swapping mics, etc..
The illustration shown below is a way to connect everything so that you can record both your instrument amplifier and a dry direct signal simultaneously.
A nice Instrument Preamp will serve as an active direct box. It will provide a high quality direct recording for use with a Reamp later. The line level Y-cord split after the Pre Amp sends a good signal to the Reamp. The Reamp converts the signal back to instrument level so that you can plug into your favorite passive guitar or bass gear just like you were plugged directly into it. You can play confortably while you capture a great direct recording for later use.
The easiest way to avoid the hum and ground loops is too distribute all your power chords from a single wall receptacle.
This provides something similar to a Star Ground scheme.
The illustration shown below illustrates a way to connect everything so that you can re-record or Reamp your audio track while experimenting with settings and equipment choices.