The fillet tool is still a problem, and it remains one. However, in the last link I showed you—about the commands currently in development for the new Rhino—they are making improvements. Click there and check all the commands that are in development.
If you have a Rhino 8 license, you can download Rhino 9 and start testing it. For example, the Patch command is no longer the same as in Rhino 8 (see the first link I gave you). Take a look at that specific discussion.
As for my method, it’s difficult to explain it here. I don’t think you live in Italy or anywhere near me, otherwise I would have gladly shown you how I approach my work in general.
And don’t ask me for video tutorials—I’m not equipped for that, and I don’t have the time to record and edit them. I only upload a few very amateur videos on YouTube, nothing more.
Unfortunately, what you’ll see in Rhino 9 won’t be available in Rhino 8. So in many situations, XNurbs is probably your best option. Yes, it can also be done with native Rhino commands, but it requires more care and time—which I assume you don’t have due to deadlines.
Take a look here: this feature was in development, and I was honestly waiting for it in Rhino 9, but it ended up being put on hold—still, it was already something.