How to remove devices properly?

Hello everyone. I have a question concerning the proper removal of connected devices. Long story short, I have an opportunity to sell some of my devices to a friend of mine and replace those devices with updated versions. I need to make sure that the devices will be completely removed from my system before we install and pair them to their system. Usually I would try to figure this out on my own either by trial and error or by lengthy research. This time is a little different as sufficient time is not available for those options. That is the reason for this post and reaching out to the experts here on the forum.

Is there an official “approved” procedure for this? Perhaps a walk through step by step or even a youtube video? I did a search and found a lot of failures and problems with removing devices in the system so I apologize if this is a revisit to a beaten topic. Just want to make sure when I install these devices in a different system that there are no issues.

I have a V1 hub and I am looking to remove 5 Zwave devices (light switches, motion sensors, door contacts and flood detectors) and 3 Zigbee devices (door contacts, motion detector). I have integrations to IFTTT and Alexa if that makes a difference. Most of these devices have multiple Smart Apps associated with them as well.

Thanks in advance