In case anyone is wondering, PSDs are also compatible with Affinity Photo. You may or may not need to enable the import of smart objects in your general settings, but I haven't tested this. As far as using this goes, it's the same as the video tutorial except in this case you'll want to erase selections from the "mask" layer in the walls group - there may be other ways but I haven't played around with this much.
Great job @Chaos!